Relicense nearly everything to Apache 2.0.

76 files changed, 887 insertions, 1322 deletions

diff --git a/Makefile.am b/Makefile.am
index b79ff77..fe56434 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -1,19 +1,17 @@
 ## Chickadee Game Toolkit
 ## Copyright © 2016 David Thompson <dthompson2@worcester.edu>
 ##
-## Chickadee is free software: you can redistribute it and/or modify
-## it under the terms of the GNU General Public License as published
-## by the Free Software Foundation, either version 3 of the License,
-## or (at your option) any later version.
+## Licensed under the Apache License, Version 2.0 (the "License");
+## you may not use this file except in compliance with the License.
+## You may obtain a copy of the License at
 ##
-## Chickadee is distributed in the hope that it will be useful, but
-## WITHOUT ANY WARRANTY; without even the implied warranty of
-## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-## General Public License for more details.
+##    http://www.apache.org/licenses/LICENSE-2.0
 ##
-## You should have received a copy of the GNU General Public License
-## along with this program.  If not, see
-## <http://www.gnu.org/licenses/>.
+## Unless required by applicable law or agreed to in writing, software
+## distributed under the License is distributed on an "AS IS" BASIS,
+## WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+## See the License for the specific language governing permissions and
+## limitations under the License.
 
 GOBJECTS = $(SOURCES:%.scm=%.go)
 
@@ -181,7 +179,7 @@ dist_shaders_DATA =				\
 
 info_TEXINFOS = doc/chickadee.texi
 doc_chickadee_TEXINFOS =			\
-  doc/fdl.texi					\
+  doc/apache-2.0.texi				\
   doc/api.texi
 
 html-local:
diff --git a/chickadee.scm b/chickadee.scm
index 476d3aa..5342e9e 100644
--- a/chickadee.scm
+++ b/chickadee.scm
@@ -2,19 +2,17 @@
 ;;; Copyright © 2018, 2021 David Thompson <dthompson2@worcester.edu>
 ;;; Copyright © 2020 Peter Elliott <pelliott@ualberta.ca>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/async-repl.scm b/chickadee/async-repl.scm
index 693b922..608bf1e 100644
--- a/chickadee/async-repl.scm
+++ b/chickadee/async-repl.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary
 ;;
diff --git a/chickadee/audio.scm b/chickadee/audio.scm
index d40d0c0..4822ec9 100644
--- a/chickadee/audio.scm
+++ b/chickadee/audio.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2020, 2019 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/audio/mpg123.scm b/chickadee/audio/mpg123.scm
index 45c319a..290dec6 100644
--- a/chickadee/audio/mpg123.scm
+++ b/chickadee/audio/mpg123.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2019 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/audio/openal.scm b/chickadee/audio/openal.scm
index 10c2bac..9cded01 100644
--- a/chickadee/audio/openal.scm
+++ b/chickadee/audio/openal.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2019 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/audio/vorbis.scm b/chickadee/audio/vorbis.scm
index a18fbf2..ab85187 100644
--- a/chickadee/audio/vorbis.scm
+++ b/chickadee/audio/vorbis.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2019 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/audio/wav.scm b/chickadee/audio/wav.scm
index b9b7c73..d5db1cb 100644
--- a/chickadee/audio/wav.scm
+++ b/chickadee/audio/wav.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2019 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/cli.scm b/chickadee/cli.scm
index 2e104fb..d0ea8df 100644
--- a/chickadee/cli.scm
+++ b/chickadee/cli.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee cli)
   #:use-module (chickadee)
diff --git a/chickadee/cli/bundle.scm b/chickadee/cli/bundle.scm
index 34b9915..4490356 100644
--- a/chickadee/cli/bundle.scm
+++ b/chickadee/cli/bundle.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee cli bundle)
   #:declarative? #f
diff --git a/chickadee/cli/play.scm b/chickadee/cli/play.scm
index e66d063..c95d1f9 100644
--- a/chickadee/cli/play.scm
+++ b/chickadee/cli/play.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee cli play)
   #:declarative? #f
diff --git a/chickadee/config.scm.in b/chickadee/config.scm.in
index 15ac1b9..211ce74 100644
--- a/chickadee/config.scm.in
+++ b/chickadee/config.scm.in
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2016 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify it
-;;; under the terms of the GNU Lesser General Public License as
-;;; published by the Free Software Foundation, either version 3 of the
-;;; License, or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but WITHOUT
-;;; ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
-;;; or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General
-;;; Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU Lesser General Public
-;;; License along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/data/array-list.scm b/chickadee/data/array-list.scm
index 65fb902..6f6bc94 100644
--- a/chickadee/data/array-list.scm
+++ b/chickadee/data/array-list.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2017 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee data array-list)
   #:use-module (chickadee utils)
diff --git a/chickadee/data/grid.scm b/chickadee/data/grid.scm
index 9f488c5..3393729 100644
--- a/chickadee/data/grid.scm
+++ b/chickadee/data/grid.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2018 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/data/heap.scm b/chickadee/data/heap.scm
index 08e473f..84b2e82 100644
--- a/chickadee/data/heap.scm
+++ b/chickadee/data/heap.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2017 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee data heap)
   #:use-module (ice-9 format)
diff --git a/chickadee/data/path-finding.scm b/chickadee/data/path-finding.scm
index cf7cc6b..adeb9d5 100644
--- a/chickadee/data/path-finding.scm
+++ b/chickadee/data/path-finding.scm
@@ -1,18 +1,16 @@
 ;;; Copyright © 2017 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/data/quadtree.scm b/chickadee/data/quadtree.scm
index 64e9b86..48f55c7 100644
--- a/chickadee/data/quadtree.scm
+++ b/chickadee/data/quadtree.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee data quadtree)
   #:use-module (chickadee math rect)
diff --git a/chickadee/data/queue.scm b/chickadee/data/queue.scm
index af13ebb..c866ce8 100644
--- a/chickadee/data/queue.scm
+++ b/chickadee/data/queue.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2017, 2018 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee data queue)
   #:use-module (ice-9 format)
diff --git a/chickadee/freetype.scm b/chickadee/freetype.scm
index df8769a..8143b41 100644
--- a/chickadee/freetype.scm
+++ b/chickadee/freetype.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2020 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/game-loop.scm b/chickadee/game-loop.scm
index 8dceb24..e70b375 100644
--- a/chickadee/game-loop.scm
+++ b/chickadee/game-loop.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2016, 2018 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee game-loop)
   #:export (run-game*
diff --git a/chickadee/graphics/9-patch.scm b/chickadee/graphics/9-patch.scm
index faf5ef9..c023b25 100644
--- a/chickadee/graphics/9-patch.scm
+++ b/chickadee/graphics/9-patch.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee graphics 9-patch)
   #:use-module (ice-9 match)
diff --git a/chickadee/graphics/blend.scm b/chickadee/graphics/blend.scm
index 2e7883f..7450c52 100644
--- a/chickadee/graphics/blend.scm
+++ b/chickadee/graphics/blend.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2016, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee graphics blend)
   #:use-module (chickadee graphics engine)
diff --git a/chickadee/graphics/buffer.scm b/chickadee/graphics/buffer.scm
index f7c8337..514f34b 100644
--- a/chickadee/graphics/buffer.scm
+++ b/chickadee/graphics/buffer.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2016-2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/graphics/color.scm b/chickadee/graphics/color.scm
index 8f11a26..c962b74 100644
--- a/chickadee/graphics/color.scm
+++ b/chickadee/graphics/color.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2016, 2018, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/graphics/depth.scm b/chickadee/graphics/depth.scm
index 6663b06..2c1e901 100644
--- a/chickadee/graphics/depth.scm
+++ b/chickadee/graphics/depth.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2020, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee graphics depth)
   #:use-module (ice-9 match)
diff --git a/chickadee/graphics/framebuffer.scm b/chickadee/graphics/framebuffer.scm
index b8af9e5..b8283af 100644
--- a/chickadee/graphics/framebuffer.scm
+++ b/chickadee/graphics/framebuffer.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2017, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/graphics/gl.scm b/chickadee/graphics/gl.scm
index 04305f3..508f244 100644
--- a/chickadee/graphics/gl.scm
+++ b/chickadee/graphics/gl.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2016, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
-;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
-;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
+;;;
+;;;    http://www.apache.org/licenses/LICENSE-2.0
+;;;
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/graphics/light.scm b/chickadee/graphics/light.scm
index 25fd17e..e941052 100644
--- a/chickadee/graphics/light.scm
+++ b/chickadee/graphics/light.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/graphics/mesh.scm b/chickadee/graphics/mesh.scm
index b00f975..8bf4f8f 100644
--- a/chickadee/graphics/mesh.scm
+++ b/chickadee/graphics/mesh.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/graphics/model.scm b/chickadee/graphics/model.scm
index 7abe460..5746e5a 100644
--- a/chickadee/graphics/model.scm
+++ b/chickadee/graphics/model.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2019, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/graphics/multisample.scm b/chickadee/graphics/multisample.scm
index d9b9dea..cd54d55 100644
--- a/chickadee/graphics/multisample.scm
+++ b/chickadee/graphics/multisample.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/graphics/particles.scm b/chickadee/graphics/particles.scm
index b089154..d8bd1b2 100644
--- a/chickadee/graphics/particles.scm
+++ b/chickadee/graphics/particles.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2018, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee graphics particles)
   #:use-module (rnrs bytevectors)
diff --git a/chickadee/graphics/path.scm b/chickadee/graphics/path.scm
index 90f5034..30d4c7c 100644
--- a/chickadee/graphics/path.scm
+++ b/chickadee/graphics/path.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2020, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary
 ;;
diff --git a/chickadee/graphics/pbr.scm b/chickadee/graphics/pbr.scm
index 22aded9..a2c7251 100644
--- a/chickadee/graphics/pbr.scm
+++ b/chickadee/graphics/pbr.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2019, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/graphics/phong.scm b/chickadee/graphics/phong.scm
index 4297d24..8812a9a 100644
--- a/chickadee/graphics/phong.scm
+++ b/chickadee/graphics/phong.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2019, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/graphics/polygon.scm b/chickadee/graphics/polygon.scm
index 6017c40..0e05018 100644
--- a/chickadee/graphics/polygon.scm
+++ b/chickadee/graphics/polygon.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2020, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary
 ;;
diff --git a/chickadee/graphics/shader.scm b/chickadee/graphics/shader.scm
index 401ff7e..f5d6c49 100644
--- a/chickadee/graphics/shader.scm
+++ b/chickadee/graphics/shader.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2016, 2019, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee graphics shader)
   #:use-module (ice-9 format)
diff --git a/chickadee/graphics/skybox.scm b/chickadee/graphics/skybox.scm
index 093f629..6de8a58 100644
--- a/chickadee/graphics/skybox.scm
+++ b/chickadee/graphics/skybox.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/graphics/sprite.scm b/chickadee/graphics/sprite.scm
index 35357dc..29c1088 100644
--- a/chickadee/graphics/sprite.scm
+++ b/chickadee/graphics/sprite.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2016, 2019, 2020, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee graphics sprite)
   #:use-module (rnrs bytevectors)
diff --git a/chickadee/graphics/stencil.scm b/chickadee/graphics/stencil.scm
index 8de4465..bc4cef2 100644
--- a/chickadee/graphics/stencil.scm
+++ b/chickadee/graphics/stencil.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2020, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee graphics stencil)
   #:use-module (ice-9 match)
diff --git a/chickadee/graphics/text.scm b/chickadee/graphics/text.scm
index d3df09a..41765d9 100644
--- a/chickadee/graphics/text.scm
+++ b/chickadee/graphics/text.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2017, 2020, 2021, 2022 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/graphics/texture.scm b/chickadee/graphics/texture.scm
index 6843120..afb1977 100644
--- a/chickadee/graphics/texture.scm
+++ b/chickadee/graphics/texture.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2016, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee graphics texture)
   #:use-module (ice-9 exceptions)
diff --git a/chickadee/graphics/tile-map.scm b/chickadee/graphics/tile-map.scm
index 04c8203..84213eb 100644
--- a/chickadee/graphics/tile-map.scm
+++ b/chickadee/graphics/tile-map.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2018, 2020, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/graphics/viewport.scm b/chickadee/graphics/viewport.scm
index 4ea44bb..e305c19 100644
--- a/chickadee/graphics/viewport.scm
+++ b/chickadee/graphics/viewport.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2017, 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/image.scm b/chickadee/image.scm
index 289fb14..48dddac 100644
--- a/chickadee/image.scm
+++ b/chickadee/image.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2023 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/image/jpeg.scm b/chickadee/image/jpeg.scm
index 4ba60fe..98a7189 100644
--- a/chickadee/image/jpeg.scm
+++ b/chickadee/image/jpeg.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/image/png.scm b/chickadee/image/png.scm
index 1d6d723..dee85b6 100644
--- a/chickadee/image/png.scm
+++ b/chickadee/image/png.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/json.scm b/chickadee/json.scm
index 9168db0..c9f1284 100644
--- a/chickadee/json.scm
+++ b/chickadee/json.scm
@@ -1,21 +1,18 @@
-;;;; json.scm --- JSON reader/writer
-;;;; Copyright © 2015, 2017 David Thompson <dthompson2@worcester.edu>
-;;;; Copyright © 2017 Christopher Allan Webber <cwebber@dustycloud.org>
-;;;;
-;;;; This library is free software; you can redistribute it and/or
-;;;; modify it under the terms of the GNU Lesser General Public
-;;;; License as published by the Free Software Foundation; either
-;;;; version 3 of the License, or (at your option) any later version.
-;;;;
-;;;; This library is distributed in the hope that it will be useful,
-;;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
-;;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;;; Lesser General Public License for more details.
-;;;;
-;;;; You should have received a copy of the GNU Lesser General Public
-;;;; License along with this library; if not, write to the Free Software
-;;;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
-;;;; 02110-1301 USA
+;;; Chickadee Game Toolkit
+;;; Copyright © 2015, 2017 David Thompson <dthompson2@worcester.edu>
+;;; Copyright © 2017 Christopher Allan Webber <cwebber@dustycloud.org>
+;;;
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
+;;;
+;;;    http://www.apache.org/licenses/LICENSE-2.0
+;;;
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee json)
   #:use-module (ice-9 match)
diff --git a/chickadee/math.scm b/chickadee/math.scm
index 64ac1f3..aa96ba8 100644
--- a/chickadee/math.scm
+++ b/chickadee/math.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2016 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee math)
   #:export (pi
diff --git a/chickadee/math/bezier.scm b/chickadee/math/bezier.scm
index f2a0d5a..86fdfed 100644
--- a/chickadee/math/bezier.scm
+++ b/chickadee/math/bezier.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2018 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/math/easings.scm b/chickadee/math/easings.scm
index 1a24dc5..6aab19a 100644
--- a/chickadee/math/easings.scm
+++ b/chickadee/math/easings.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2017 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee math easings)
   #:use-module (chickadee math)
diff --git a/chickadee/math/matrix.scm b/chickadee/math/matrix.scm
index d8294b0..a77fd20 100644
--- a/chickadee/math/matrix.scm
+++ b/chickadee/math/matrix.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2016 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee math matrix)
   #:use-module (ice-9 format)
diff --git a/chickadee/math/quaternion.scm b/chickadee/math/quaternion.scm
index 1f7c27b..064a648 100644
--- a/chickadee/math/quaternion.scm
+++ b/chickadee/math/quaternion.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2017 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/math/rect.scm b/chickadee/math/rect.scm
index 2fb925b..cc99fb0 100644
--- a/chickadee/math/rect.scm
+++ b/chickadee/math/rect.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2016 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee math rect)
   #:use-module (ice-9 format)
diff --git a/chickadee/math/vector.scm b/chickadee/math/vector.scm
index 49bea5a..9222ed5 100644
--- a/chickadee/math/vector.scm
+++ b/chickadee/math/vector.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2016 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee math vector)
   #:use-module (ice-9 format)
diff --git a/chickadee/pixbuf.scm b/chickadee/pixbuf.scm
index 61af06f..c15a0b7 100644
--- a/chickadee/pixbuf.scm
+++ b/chickadee/pixbuf.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2023 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/chickadee/readline.scm b/chickadee/readline.scm
index ff370e8..317642e 100644
--- a/chickadee/readline.scm
+++ b/chickadee/readline.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary
 ;;
diff --git a/chickadee/scripting.scm b/chickadee/scripting.scm
index 30a2d04..e7ecce0 100644
--- a/chickadee/scripting.scm
+++ b/chickadee/scripting.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2017, 2020 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee scripting)
   #:use-module (chickadee game-loop)
diff --git a/chickadee/scripting/agenda.scm b/chickadee/scripting/agenda.scm
index c69a7a9..ffa9b5e 100644
--- a/chickadee/scripting/agenda.scm
+++ b/chickadee/scripting/agenda.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2017, 2020 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee scripting agenda)
   #:use-module (chickadee data heap)
diff --git a/chickadee/scripting/channel.scm b/chickadee/scripting/channel.scm
index 6b3901a..66855b2 100644
--- a/chickadee/scripting/channel.scm
+++ b/chickadee/scripting/channel.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2017, 2018 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee scripting channel)
   #:use-module (chickadee data queue)
diff --git a/chickadee/scripting/script.scm b/chickadee/scripting/script.scm
index 1e07278..be996bb 100644
--- a/chickadee/scripting/script.scm
+++ b/chickadee/scripting/script.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2017 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee scripting script)
   #:use-module (ice-9 format)
diff --git a/chickadee/utils.scm b/chickadee/utils.scm
index f833b08..1b1f751 100644
--- a/chickadee/utils.scm
+++ b/chickadee/utils.scm
@@ -2,19 +2,17 @@
 ;;; Copyright (C) 2014 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2016 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (chickadee utils)
   #:use-module (ice-9 match)
diff --git a/doc/apache-2.0.texi b/doc/apache-2.0.texi
new file mode 100644
index 0000000..5866709
--- /dev/null
+++ b/doc/apache-2.0.texi
@@ -0,0 +1,214 @@
+         Apache License
+
+   Version 2.0, January 2004
+
+@uref{http://www.apache.org/licenses/}
+
+TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION
+
+@enumerate
+@item
+Definitions.
+
+``License'' shall mean the terms and conditions for use, reproduction,
+and distribution as defined by Sections 1 through 9 of this document.
+
+``Licensor'' shall mean the copyright owner or entity authorized by
+the copyright owner that is granting the License.
+
+``Legal Entity'' shall mean the union of the acting entity and all
+other entities that control, are controlled by, or are under common
+control with that entity. For the purposes of this definition,
+``control'' means (i) the power, direct or indirect, to cause the
+direction or management of such entity, whether by contract or
+otherwise, or (ii) ownership of fifty percent (50%) or more of the
+outstanding shares, or (iii) beneficial ownership of such entity.
+
+``You'' (or ``Your'') shall mean an individual or Legal Entity
+exercising permissions granted by this License.
+
+``Source'' form shall mean the preferred form for making modifications,
+including but not limited to software source code, documentation
+source, and configuration files.
+
+``Object'' form shall mean any form resulting from mechanical
+transformation or translation of a Source form, including but
+not limited to compiled object code, generated documentation,
+and conversions to other media types.
+
+``Work'' shall mean the work of authorship, whether in Source or
+Object form, made available under the License, as indicated by a
+copyright notice that is included in or attached to the work
+(an example is provided in the Appendix below).
+
+``Derivative Works'' shall mean any work, whether in Source or Object
+form, that is based on (or derived from) the Work and for which the
+editorial revisions, annotations, elaborations, or other modifications
+represent, as a whole, an original work of authorship. For the purposes
+of this License, Derivative Works shall not include works that remain
+separable from, or merely link (or bind by name) to the interfaces of,
+the Work and Derivative Works thereof.
+
+``Contribution'' shall mean any work of authorship, including
+the original version of the Work and any modifications or additions
+to that Work or Derivative Works thereof, that is intentionally
+submitted to Licensor for inclusion in the Work by the copyright owner
+or by an individual or Legal Entity authorized to submit on behalf of
+the copyright owner. For the purposes of this definition, ``submitted''
+means any form of electronic, verbal, or written communication sent
+to the Licensor or its representatives, including but not limited to
+communication on electronic mailing lists, source code control systems,
+and issue tracking systems that are managed by, or on behalf of, the
+Licensor for the purpose of discussing and improving the Work, but
+excluding communication that is conspicuously marked or otherwise
+designated in writing by the copyright owner as ``Not a Contribution.''
+
+``Contributor'' shall mean Licensor and any individual or Legal Entity
+on behalf of whom a Contribution has been received by Licensor and
+subsequently incorporated within the Work.
+
+@item
+Grant of Copyright License. Subject to the terms and conditions of
+this License, each Contributor hereby grants to You a perpetual,
+worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+copyright license to reproduce, prepare Derivative Works of,
+publicly display, publicly perform, sublicense, and distribute the
+Work and such Derivative Works in Source or Object form.
+
+@item
+Grant of Patent License. Subject to the terms and conditions of
+this License, each Contributor hereby grants to You a perpetual,
+worldwide, non-exclusive, no-charge, royalty-free, irrevocable
+(except as stated in this section) patent license to make, have made,
+use, offer to sell, sell, import, and otherwise transfer the Work,
+where such license applies only to those patent claims licensable
+by such Contributor that are necessarily infringed by their
+Contribution(s) alone or by combination of their Contribution(s)
+with the Work to which such Contribution(s) was submitted. If You
+institute patent litigation against any entity (including a
+cross-claim or counterclaim in a lawsuit) alleging that the Work
+or a Contribution incorporated within the Work constitutes direct
+or contributory patent infringement, then any patent licenses
+granted to You under this License for that Work shall terminate
+as of the date such litigation is filed.
+
+@item
+Redistribution. You may reproduce and distribute copies of the
+Work or Derivative Works thereof in any medium, with or without
+modifications, and in Source or Object form, provided that You
+meet the following conditions:
+
+(a) You must give any other recipients of the Work or
+    Derivative Works a copy of this License; and
+
+(b) You must cause any modified files to carry prominent notices
+    stating that You changed the files; and
+
+(c) You must retain, in the Source form of any Derivative Works
+    that You distribute, all copyright, patent, trademark, and
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+    excluding those notices that do not pertain to any part of
+    the Derivative Works; and
+
+(d) If the Work includes a ``NOTICE'' text file as part of its
+    distribution, then any Derivative Works that You distribute must
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+    pertain to any part of the Derivative Works, in at least one
+    of the following places: within a NOTICE text file distributed
+    as part of the Derivative Works; within the Source form or
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+    within a display generated by the Derivative Works, if and
+    wherever such third-party notices normally appear. The contents
+    of the NOTICE file are for informational purposes only and
+    do not modify the License. You may add Your own attribution
+    notices within Derivative Works that You distribute, alongside
+    or as an addendum to the NOTICE text from the Work, provided
+    that such additional attribution notices cannot be construed
+    as modifying the License.
+
+You may add Your own copyright statement to Your modifications and
+may provide additional or different license terms and conditions
+for use, reproduction, or distribution of Your modifications, or
+for any such Derivative Works as a whole, provided Your use,
+reproduction, and distribution of the Work otherwise complies with
+the conditions stated in this License.
+
+@item
+Submission of Contributions. Unless You explicitly state otherwise,
+any Contribution intentionally submitted for inclusion in the Work
+by You to the Licensor shall be under the terms and conditions of
+this License, without any additional terms or conditions.
+Notwithstanding the above, nothing herein shall supersede or modify
+the terms of any separate license agreement you may have executed
+with Licensor regarding such Contributions.
+
+@item
+Trademarks. This License does not grant permission to use the trade
+names, trademarks, service marks, or product names of the Licensor,
+except as required for reasonable and customary use in describing the
+origin of the Work and reproducing the content of the NOTICE file.
+
+@item
+Disclaimer of Warranty. Unless required by applicable law or
+agreed to in writing, Licensor provides the Work (and each
+Contributor provides its Contributions) on an ``AS IS'' BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
+implied, including, without limitation, any warranties or conditions
+of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A
+PARTICULAR PURPOSE@. You are solely responsible for determining the
+appropriateness of using or redistributing the Work and assume any
+risks associated with Your exercise of permissions under this License.
+
+@item
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+negligent acts) or agreed to in writing, shall any Contributor be
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+@item
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+the Work or Derivative Works thereof, You may choose to offer,
+and charge a fee for, acceptance of support, warranty, indemnity,
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+defend, and hold each Contributor harmless for any liability
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+of your accepting any such warranty or additional liability.
+@end enumerate
+
+END OF TERMS AND CONDITIONS
+
+APPENDIX: How to apply the Apache License to your work.
+
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+boilerplate notice, with the fields enclosed by brackets ``[]''
+replaced with your own identifying information. (Don't include
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+
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diff --git a/doc/chickadee.texi b/doc/chickadee.texi
index f246cfb..7c7e469 100644
--- a/doc/chickadee.texi
+++ b/doc/chickadee.texi
@@ -4,7 +4,7 @@
 @settitle The Chickadee Game Toolkit
 @c %**end of header
 @copying
-Copyright @copyright{} 2017-2021  David Thompson @email{dthompson2@@worcester.edu}
+Copyright @copyright{} 2017-2023  David Thompson @email{dthompson2@@worcester.edu}
 
 @quotation
 Permission is granted to copy, distribute and/or modify this document
@@ -55,7 +55,7 @@ The document was typeset with
 * Command Line Interface::      Run Chickadee programs from the terminal.
 * Live Coding::                 Tips for building games from the REPL.
 * API Reference::               Chickadee API reference.
-* Copying This Manual::         The GNU Free Documentation License and you!
+* Copying This Manual::
 * Index::
 @end menu
 
@@ -492,13 +492,14 @@ Guile.  Use @code{M-x connect-to-guile} to connect to the REPL server.
 @appendix Copying This Manual
 
 @menu
-* GNU Free Documentation License::  License for copying this manual.
+* Apache 2.0 License::  License for copying this manual.
 @end menu
 
 @c Get fdl.texi from http://www.gnu.org/licenses/fdl.html
-@node GNU Free Documentation License
-@section GNU Free Documentation License
-@include fdl.texi
+@node Apache 2.0 License
+@section Apache 2.0 License
+
+@include apache-2.0.texi
 
 @node Index
 @unnumbered Index
diff --git a/doc/fdl.texi b/doc/fdl.texi
deleted file mode 100644
index 9c3bbe5..0000000
--- a/doc/fdl.texi
+++ /dev/null
@@ -1,505 +0,0 @@
-@c The GNU Free Documentation License.
-@center Version 1.3, 3 November 2008
-
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diff --git a/guix.scm b/guix.scm
index 5d3e529..e2af881 100644
--- a/guix.scm
+++ b/guix.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2016 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify it
-;;; under the terms of the GNU General Public License as published by
-;;; the Free Software Foundation, either version 3 of the License, or
-;;; (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but WITHOUT
-;;; ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
-;;; or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public
-;;; License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 ;;; Commentary:
 ;;
diff --git a/pre-inst-env.in b/pre-inst-env.in
index ff815aa..5da2288 100644
--- a/pre-inst-env.in
+++ b/pre-inst-env.in
@@ -3,18 +3,17 @@
 # Chickadee Game Toolkit
 # Copyright © 2016 David Thompson <dthompson2@worcester.edu>
 #
-# Chickadee is free software: you can redistribute it and/or modify it
-# under the terms of the GNU General Public License as published by
-# the Free Software Foundation, either version 3 of the License, or
-# (at your option) any later version.
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
 #
-# Chickadee is distributed in the hope that it will be useful, but
-# WITHOUT ANY WARRANTY; without even the implied warranty of
-# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-# General Public License for more details.
+#    http://www.apache.org/licenses/LICENSE-2.0
 #
-# You should have received a copy of the GNU General Public License
-# along with Chickadee.  If not, see <http://www.gnu.org/licenses/>.
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
 
 abs_top_srcdir="`cd "@abs_top_srcdir@" > /dev/null; pwd`"
 abs_top_builddir="`cd "@abs_top_builddir@" > /dev/null; pwd`"
diff --git a/scripts/chickadee.in b/scripts/chickadee.in
index d7e26fe..5194436 100644
--- a/scripts/chickadee.in
+++ b/scripts/chickadee.in
@@ -4,18 +4,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software; you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation; either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with Chickadee.  If not, see <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (use-modules (chickadee cli))
 
diff --git a/tests/array-list.scm b/tests/array-list.scm
index a260c9b..58851df 100644
--- a/tests/array-list.scm
+++ b/tests/array-list.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (tests array-list)
   #:use-module (tests utils)
diff --git a/tests/heap.scm b/tests/heap.scm
index 5b179c5..6d43d33 100644
--- a/tests/heap.scm
+++ b/tests/heap.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (tests heap)
   #:use-module (tests utils)
diff --git a/tests/matrix.scm b/tests/matrix.scm
index 0cd24a9..ec6209a 100644
--- a/tests/matrix.scm
+++ b/tests/matrix.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2022 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (tests matrix)
   #:use-module (tests utils)
diff --git a/tests/quadtree.scm b/tests/quadtree.scm
index b3772e2..ee94ebb 100644
--- a/tests/quadtree.scm
+++ b/tests/quadtree.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (tests quadtree)
   #:use-module (tests utils)
diff --git a/tests/queue.scm b/tests/queue.scm
index fac2df4..fd4d6f7 100644
--- a/tests/queue.scm
+++ b/tests/queue.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (tests queue)
   #:use-module (tests utils)
diff --git a/tests/rect.scm b/tests/rect.scm
index 6da72fc..6b9a745 100644
--- a/tests/rect.scm
+++ b/tests/rect.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2022 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (tests rect)
   #:use-module (tests utils)
diff --git a/tests/utils.scm b/tests/utils.scm
index 684fcd4..1a3e3ad 100644
--- a/tests/utils.scm
+++ b/tests/utils.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (tests utils)
   #:use-module (srfi srfi-64)
diff --git a/tests/vector.scm b/tests/vector.scm
index 1a578d4..abc2da8 100644
--- a/tests/vector.scm
+++ b/tests/vector.scm
@@ -1,19 +1,17 @@
 ;;; Chickadee Game Toolkit
 ;;; Copyright © 2021 David Thompson <dthompson2@worcester.edu>
 ;;;
-;;; Chickadee is free software: you can redistribute it and/or modify
-;;; it under the terms of the GNU General Public License as published
-;;; by the Free Software Foundation, either version 3 of the License,
-;;; or (at your option) any later version.
+;;; Licensed under the Apache License, Version 2.0 (the "License");
+;;; you may not use this file except in compliance with the License.
+;;; You may obtain a copy of the License at
 ;;;
-;;; Chickadee is distributed in the hope that it will be useful, but
-;;; WITHOUT ANY WARRANTY; without even the implied warranty of
-;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-;;; General Public License for more details.
+;;;    http://www.apache.org/licenses/LICENSE-2.0
 ;;;
-;;; You should have received a copy of the GNU General Public License
-;;; along with this program.  If not, see
-;;; <http://www.gnu.org/licenses/>.
+;;; Unless required by applicable law or agreed to in writing, software
+;;; distributed under the License is distributed on an "AS IS" BASIS,
+;;; WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+;;; See the License for the specific language governing permissions and
+;;; limitations under the License.
 
 (define-module (tests vector)
   #:use-module (tests utils)