Licence

Tandem is free and open-source software under the GNU Affero General Public License, version 3 only (AGPL-3.0-only). The full text is in LICENSE.

What that means for you

• Run it for any purpose, privately or for other people, without paying anyone.
• Read, modify and share the source. Changes you distribute carry the same licence.
• Section 13 — the network clause. If you run a modified Tandem as a service other people use, they are entitled to the source of your modified version. Running it unmodified, or modifying it only for yourself, creates no such obligation.

The choice follows the project's own dependencies: Tandem builds on AGPL and GPL libraries, so it cannot be released under weaker terms.

Third-party components

Tandem builds on open-source libraries that keep their own licences — Readium and Media3 on Android, epub.js and React on the web, FastAPI, SQLAlchemy and faster-whisper on the server, and ffmpeg for media. The dependency manifests in the repository list them.

The books are not covered

The licence covers Tandem's code, not the content you put in it. Your library stays yours, on your own server.