Credits & licenses

FlexiChess is built on the work of others. Game data and core software below are used with permission or under their open-source licenses, with thanks.

Game data

• Lumbra's Gigabase — Reference game database © Michael Jansen. Used under a commercial license; base collection released under CC BY-NC-SA 4.0.
• The Week in Chess (TWIC) — Current tournament games by Mark Crowther, used to keep the database up to date.

Software

• Stockfish — Chess engine analysis. Licensed under the GNU General Public License v3.
• Chessground — Board and move UI by the Lichess team. Licensed under the GNU General Public License v3.
• chess.js — Move generation and validation. BSD 2-Clause license.
• ts-fsrs — Spaced-repetition scheduling for repertoire training. MIT license.

Stockfish and Chessground are distributed under the GNU GPL v3; FlexiChess includes them in compliance with that license. Trademarks and game data remain the property of their respective owners. FlexiChess is not affiliated with or endorsed by these projects.