Credits & licenses
Multi Chess is built on excellent open-source work. Thank you to all authors.
Multi Chess itself is free software by Jan-Maurice Dahlmanns (Bugfish), licensed under the GNU General Public License v3.0 or later. You may use, study, share and change it under the terms of that license. The browser code is delivered to you unminified, and the complete source code is published on GitHub; it is also available on request via the contact details in the Impressum.
The game was developed with the help of Claude Code, Anthropic's AI coding assistant.
Software
| Component | Used for | License |
|---|---|---|
| chessground by the lichess.org team | Interactive chess board | GPL-3.0-or-later |
| chessops by Niklas Fiekas | Chess and variant rules, move validation, SAN, FEN | GPL-3.0-or-later |
| Stockfish 19 by the Stockfish developers, WebAssembly build Stockfish.js by Nathan Rugg / Chess.com | Computer opponent, coach, analysis and game review (runs in your browser) | GPL-3.0 |
| Socket.IO | Real-time connection to the game server | MIT |
| Express | Web server | MIT |
| Nodemailer by Andris Reinman | Sending the account e-mails | MIT-0 |
| Node.js (including its built-in SQLite) | Server runtime and account database | MIT (SQLite: public domain) |
| @badrap/result | Dependency of chessops | MIT |
Data
| Data | Source | License |
|---|---|---|
| Opening names (about 3,800 openings) | lichess-org/chess-openings | CC0-1.0 (public domain) |
| “Opera Game” on the start page | Paul Morphy vs. Duke Karl of Brunswick and Count Isouard, Paris 1858 | Historical game (public domain) |
Piece sets
| Set | Author | License |
|---|---|---|
| Classic | Colin M. L. Burnett (“cburnett”), as distributed with chessground | GPL-2.0-or-later (also available under BSD and GFDL) |
| Merida | Armando Hernandez Marroquin, via lichess.org | GPL-2.0-or-later |
| Chessnut | Alexis Luengas, via lichess.org | Apache-2.0 |
| Fantasy | Maurizio Monge, via lichess.org | MIT |
The license texts are included with the source code (LICENSE and public/pieces/*/LICENSE.txt).
Everything else
Board themes, icons, sounds (synthesised in your browser), logo, texts and the game server were made for this project and are part of the GPL-licensed source code.
Last updated: 2026-09-30