Licenses
ChessClerk's own code and content belong to Clerk Suite LLC. These parts were made by others, and each keeps its own license.
Shipped with ChessClerk (they run in your browser)
- Stockfish 19 (the "lite" web builds), the chess engine. GNU General Public License version 3. License text.
- Maia 3 (the simplified model, maia3_simplified.onnx), which plays as the human-like engine. GNU General Public License version 3. License text.
- ONNX Runtime Web, which runs the Maia model. MIT License. License text.
- Chess pieces by Colin M.L. Burnett ("Cburnett"). Creative Commons Attribution-ShareAlike 3.0. License text.
- Lichess puzzles (the puzzle collection). Released by Lichess under Creative Commons CC0 (no rights reserved).
Source offer
The GPLv3 lets you have the complete source of Stockfish and Maia as shipped here. Stockfish's source is at github.com/official-stockfish/Stockfish and Maia's at github.com/CSSLab. You can also ask for it at chessclerk@gmail.com, and we'll send it.
Services ChessClerk asks (nothing of theirs is shipped)
- Lichess tablebase (tablebase.lichess.ovh): perfect endgame answers for 7 pieces or fewer.
- Wikipedia: opening and player articles, shown as plain text and credited with a link, as its CC BY-SA license asks.
- Chess.com and Lichess: your public games, when you import them.
- Anthropic and Google: the AI models that answer the clerk, through our server.
- Google Firebase (sign-in and coaching classes), Cloudflare (our server) and Stripe (payments).
ChessClerk is not affiliated with Lichess, Chess.com, Wikipedia or any of these companies.
Game data
The opening counts and evaluations come from our own Stockfish work over public game collections: The Week in Chess, the Lichess open database (CC0) and others.