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Licensing

Capycal is licensed under the GPL-3.0-only (LICENSE), while contributions come in under the MIT License (CONTRIBUTING.md, confirmed in the pull request template). This page explains why, so the setup is not changed by accident.

Why the GPL

App store terms (Apple’s in particular) are widely read as incompatible with the GPL; the FSF holds this view, and VLC was removed from the App Store over it in 2011. So nobody but the copyright holder can ship a copy of Capycal to an app store. The maintainer, who owns the copyright to their own code, can. No court has decided this, so it is a practical protection, not a legal guarantee; clones have to be found and reported to the store.

Why contributions are MIT

A contributor keeps the copyright to their code and only licenses it. Code contributed under the GPL could not go into an app store build without breaking the contributor’s license: they could demand it be taken down and claim damages. Under the MIT License the maintainer may ship it anywhere, including app stores and a later change of the project’s license.

Under German copyright law an author has a claim to fair remuneration (§ 32 UrhG) and, for a big success, to more afterwards (§ 32a UrhG). Both claims do not exist when the author grants a simple right of use to everyone free of charge (§ 32 Abs. 3 Satz 3, § 32a Abs. 3 Satz 3, the “Linux clause”). The MIT License is such a grant, so a paid build owes contributors nothing.

How a contribution comes inRemuneration claimIn an app store buildLater relicensing
GPL (a pull request merged as is)nonono
MIT (the project’s way)noyesyes
A CLA granting rights to the maintainer onlypossibleyesyes

BSD, ISC, 0BSD and Apache-2.0 would work like MIT here, they also grant rights to everyone for free. They differ only in their duties (notices, Apache’s NOTICE file and patent grant). MIT keeps it simplest.

Rules that follow

  • Every contribution needs the MIT confirmation of the pull request template and a line in CONTRIBUTORS.md, whose notices every package ships.
  • No CLA that grants rights only to the maintainer: it would bring back the remuneration claim.
  • Contributed portions can be reused by anyone under MIT. That is fine as long as most of Capycal is the maintainer’s GPL code; a clone of the app still needs it.
  • No GPL or LGPL crate may be compiled into the binaries, or the app store build breaks. about.toml lists the accepted licenses and make check-notices (run by CI) rejects any other; decide before adding one. GTK and libadwaita are system libraries of the Linux app only.

This is a reading of the law, not legal advice; have the wording of CONTRIBUTING.md checked before the first store release.