ADR 0003 Licence

ADR-0003: GPL-3.0 with an App Store Distribution Exception

Source of truth: this wiki page.

• Status: Superseded by ADR-0040, which keeps this decision for the app's code unchanged and licenses deck content under CC BY-SA 4.0.
• Date: 2026-09-19

Context

Three goals, stated in priority order:

1. Nobody may close a fork. Derivatives must stay open.
2. Nobody should profit from selling it, though donations for genuine added value are fine.
3. It must be distributable through both the Play Store and the App Store.

Decision

Licence under GPL-3.0 plus an additional permission under section 7 permitting distribution through app stores whose terms would otherwise conflict. The exception text is in LICENSE-EXCEPTION.md.

Reasoning

Goal 1 requires strong copyleft. GPL-3.0 delivers it: any distributed derivative must be released under GPL-3.0 in full. MPL-2.0 was considered and rejected as too weak — its copyleft is per file, so a fork can combine Fluenough's files with proprietary code and ship a largely closed product.

Goal 2 cannot be achieved by any open source licence, and is not attempted. The right to sell copies is a defining requirement of both the Open Source Definition and the Free Software Definition; GPL-3.0 §4 states it explicitly. A licence forbidding sale would not be open source, would be rejected by F-Droid, and would deter contributors.

Copyleft achieves the practical effect through a different mechanism: anyone may sell Fluenough, but every purchaser immediately receives the source and the right to redistribute it freely. A seller cannot stop their own customers from giving it away. The commercial value of selling freely-redistributable copies collapses toward zero. This is by design, not a loophole.

Non-commercial licences (PolyForm Noncommercial, Prosperity) were considered and rejected: not open source, rejected by F-Droid, and "commercial" is ambiguous to enforce.

Goal 3 requires the exception. GPL-3.0 §§7 and 10 forbid "further restrictions"; Apple's App Store terms impose device limits and DRM that qualify. GNU Go was removed from the App Store in 2010 over exactly this, and VLC had to relicense to ship on iOS. The Play Store does not have this problem — it is specific to Apple.

The section 7 additional permission is an established remedy for this, used by other GPL/AGPL mobile projects. It waives only the distribution-channel conflict and leaves every copyleft obligation intact.

AGPL-3.0 was considered and rejected. Its network clause targets the SaaS loophole, which cannot trigger for an offline mobile app, so it would add contributor friction for a protection that never applies.

Consequences

Forks must stay open. Selling is legal but commercially pointless. The app can ship on F-Droid, the Play Store and the App Store.

No CLA is required. The exception is part of the project licence from the first commit, so all contributions are made under GPL-3.0-with-exception automatically. This matters for a project whose deck content arrives as pull requests.

The licence cannot be changed later without the agreement of every contributor. This is accepted deliberately.

The name "Fluenough" is not licensed. Copyleft permits anyone to fork the code; trademark is the separate instrument that stops a fork passing itself off as the original.

See also: Contributing · ADR-Index · Home