JOY's chess engine is Stockfish, a free and open-source chess engine.

These two files are Stockfish.js 19.0.0, the "lite single-threaded" build,
copied unmodified from the npm package stockfish@19.0.0:

  stockfish-19-lite-single.js
  stockfish-19-lite-single.wasm

Stockfish and Stockfish.js are distributed under the GNU General Public
License, version 3 (see COPYING.txt in this folder). The corresponding
source code is available from:

  Stockfish.js 19.0.0:  https://github.com/nmrugg/stockfish.js/tree/v19.0.0
  Stockfish:            https://github.com/official-stockfish/Stockfish