Engines and licences

Engine and open-source notices

Play is the existing Shatranj app. This course does not ship a second copy of those engines. The labels below match the engines that app actually runs.

Shatranj, original alpha-beta, MIT, copyright Vinod Naraniwal. Source stays in the Play app under src/lib/chess/shatranj-engine.mjs. It is not derived from Stockfish.
Stockfish 19, GPL, stockfishchess.org, via stockfish.js. Running in the Play tab. Analysis trusts this build when engines disagree.
Fairy-Stockfish, GPL, fairy-stockfish.wasm. Running in the Play tab for a second line and variants. It is not the same search as Stockfish 19.
Maia 3, 5-million-parameter net, AGPL, University of Toronto CSSLab, via maia3-js. Running in the Play tab as a human-move opponent, not as the strongest move.
Leela label in Play runs Lichess zerofish with the TinyGyal-8 network. It is a small CPU net, not a current Lc0 rating-list network.

Komodo, Torch, Ethereal, Arasan, Crafty, Houdini, and Fritz are described in Play as closed or not bundled. They are not selectable opponents.

chess.js is BSD-2-Clause and is the rules layer for this course. Names are used so the notices can be checked. They are not endorsements.