CUPS is developed by Apple Inc. and distributed as open source software under the Apache License, Version 2.0 with exceptions to allow linking to GPL2/LGPL2 code. Significant contributions to CUPS must be licensed to Apple using the Apple Contributor Agreement:
Contributions should be submitted as attachments to bug reports on the CUPS Github project. Changes to existing source files should be submitted as unified diffs while new source files should be provided as-is or in an archive. Github pull requests can also be used to submit changes.