Schach-Engine für „Schach gegen den Computer“ – GPL-3.0 (Source Code / Quelltext)
Chess engine used by "Play chess against the computer" – GPL-3.0

Engine: Stockfish.js 19, "lite single-threaded" build (c) 2026 Chess.com, LLC, https://github.com/nmrugg/stockfish.js
        based on Stockfish (c) T. Romstad, M. Costalba, J. Kiiski, G. Linscott and other contributors,
        https://github.com/official-stockfish/Stockfish ; lite net nn-61e7af4bb97d by Chris Bao (sscg13).
License: GNU General Public License v3 – full text: /vendor/stockfish/Copying.txt ; authors: /vendor/stockfish/AUTHORS.txt

Distributed unmodified, taken from npm package stockfish@19.0.0
(integrity sha512-jDyYLbqNpboQcMs5HodTHI2CrKL74zkQWb1+sgoNXw5HI6avTblW4G0X7afFt3BBOc6VbTSkOV64EUxm/DWSpg==):
  stockfish-19-lite-single.js    SHA-256 d3344124ab067fb0b90ee77873bb8e9fbf5fc01bc525fe714b0f942581e889e6
  stockfish-19-lite-single.wasm  SHA-256 57ac2d72312aba346760e3f173f687a8c211208e97a87268436f7f0e10bb5387

Corresponding Source (GPLv3 section 6) – hosted on this website:
  /vendor/stockfish/quelle/stockfish.js-54fde71d90c7c403964f6cacef48f7bbec495df1.tar.gz
     = https://github.com/nmrugg/stockfish.js at commit 54fde71d90c7c403964f6cacef48f7bbec495df1 (gitHead of
       stockfish@19.0.0), incl. Stockfish C++ sources, build.js and Emscripten settings
     SHA-256 ff4955eb2b2c6e49152dee875b28794be58cf52a8f019bcb230251207dbdce09
  /vendor/stockfish/quelle/nn-61e7af4bb97d.nnue  (embedded lite network, SHA-256 61e7af4bb97d51ee…6f99e5b)
Build: install emscripten 3.1.7, put the .nnue file into src/, then  ./build.js --only-lite-single  (see README.md in the archive).

How the website uses it: the engine runs as a separate program in its own Web Worker and only exchanges UCI text
commands with the page (e.g. "position startpos moves e2e4", "go movetime 500" → "bestmove e7e5").
The page's own code (board, rules, interface) is not derived from Stockfish.