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LEGAL

Open-Source Attributions

The shoulders we stand on.

Bright Moves is grateful to the open-source community. This product includes software under permissive and copyleft licenses, including:

Stockfish
chess engine evaluation (GPL v3)
Lichess puzzle database (CC0)
Lichess master games database (CC0)
Staunton SVG chess piece set — Cburnett (GPL v2+)
Fantasy chess piece set — Maurizio Monge (MIT)
Spatial chess piece set — Maurizio Monge (MIT)
Celtic chess piece set — Maurizio Monge (MIT)
Chessnut chess piece set — Alexis Luengas (Apache 2.0)
Firi chess piece set — James Faure (CC BY 4.0)
React, Next.js & the wider JS ecosystem (MIT)

Per the GPL, corresponding source for GPL-licensed components is available on request. Full license texts ship with the application.

Stockfish

Position evaluation in the analysis workbench is powered by Stockfish, a free and strong UCI chess engine derived from Glaurung 2.1. We self-host Stockfish on our own infrastructure for full control over the eval pipeline and zero dependency on third-party uptime.

Stockfish is distributed under the GPL-3.0, which permits modification and redistribution under the same license. Bright Moves uses an unmodified, official Stockfish binary release, run only as a separate process over the UCI text protocol — it is not linked into any Bright Moves code, so the GPL's copyleft does not extend to our own software. Serving evaluations over HTTP is not itself conveyance; however, we package the Stockfish binary inside a container image that we transfer between our systems, which is conveyance of object code under GPL-3.0 §6. Accordingly we provide the Corresponding Source and a written offer for it — see “GPL-3.0 source & written offer” below.

Lc0 (Leela Chess Zero)

The human-like AI opponent is played by Lc0 (Leela Chess Zero), a neural-network chess engine, run as a separate process over UCI on our own infrastructure (it executes the Maia networks below). It is not linked into any Bright Moves code.

We use Lc0 unmodified. Because we convey it inside a container image, we provide its Corresponding Source and a written offer — see “GPL-3.0 source & written offer” below.

Maia Chess (maia-chess)

The opponent's human-like move choices come from the Maia Chess neural networks — models trained to play like humans at specific rating levels, by the Computational Social Science Lab (CSSLab) at the University of Toronto, together with Microsoft Research. The weight files themselves are the GPL-3.0 source form (no build reproduces a trained network).

We use the Maia weight files unmodified. Because we convey them inside a container image, we provide the Corresponding Source and a written offer — see below.

GPL-3.0 source & written offer

Stockfish, Lc0, and the Maia networks above are licensed under the GNU General Public License, version 3. Bright Moves packages these programs inside container images that we transfer between our systems, which is conveyance of object code under GPL-3.0 §6. To comply, we make the following written offer:

For at least three (3) years from the date we last conveyed the container image, we will give any third party who possesses the object code a complete machine-readable copy of the Corresponding Source for the GPL-3.0 components (Lc0, the Maia weight files, and Stockfish), for no more than our reasonable cost of physically performing the conveyance, or equivalent no-charge access to download it. The source corresponds to the exact pinned versions we ship (Lc0 v0.31.2; Maia v1.0 bands 1100/1300/1500/1700/1900; Stockfish 17.1). To request it, email legal at algebrics.com with the subject “GPL-3.0 Corresponding Source request — Brightmoves engine images”.

The same offer, the full GPL-3.0 license text, a copyright NOTICE, a pinned-hash source manifest, and a fetch/verify script are also shipped inside each engine image at /usr/share/doc/brightmoves-gpl/. We use all three programs unmodified (separate-process / UCI invocation only); no GPL-3.0 §5 modified-source obligation arises.

Staunton SVG chess piece set (Cburnett)

The default chess pieces (and the geometry behind the gradient Staunton set) are the Staunton SVG chess piece set created by Colin M. L. Burnett (“Cburnett”) — the widely-used set Lichess ships. We render the set with our own gradient fills and outline treatment; the piece geometry is Cburnett's.

GPL v2+ is a copyleft license: our adaptation of these pieces (the gradient-filled Staunton set used in this app) is likewise made available under GPL v2+; corresponding source is available on request (see the written offer above), with attribution to the original author preserved here.

Fantasy, Spatial & Celtic chess piece sets (Maurizio Monge)

Three of the optional piece styles — Fantasy, Spatial, and Celtic — are by Maurizio Monge, distributed with Lichess. We ship the original SVGs unmodified.

The MIT License permits use, copying, and distribution provided the copyright notice and permission notice are preserved; they are retained with the bundled assets and acknowledged here.

Chessnut chess piece set (Alexis Luengas)

The Chessnut piece style is by Alexis Luengas, distributed with Lichess. We ship the original SVGs unmodified.

The Apache License 2.0 requires that we retain the copyright, license, and any NOTICE text from the source; those are preserved with the bundled assets and the attribution is given here.

Firi chess piece set (James Faure)

The Firi piece style is by James Faure, distributed with Lichess. We ship the original SVGs unmodified.

CC BY 4.0 permits use and distribution (including commercially) provided the author is credited; attribution to James Faure is given here.

chess.js

Move generation, validation, and PGN parsing in the browser are handled by chess.js, licensed under the BSD 2-Clause License.

react-chessboard

The interactive board UI is react-chessboard, licensed under the MIT License.

Chess puzzles (Lichess open puzzle database)

Bright Moves puzzles are seeded from the Lichess open puzzle database, generated from games played on Lichess. This data is dedicated to the public domain under the Creative Commons CC0 1.0 Universal Public Domain Dedication. Lichess does not require attribution; we credit them gratefully. Lichess is free/libre open-source software. Bright Moves is not affiliated with or endorsed by Lichess.

Master games database (Lichess)

The Bright Moves “Master DB” games explorer is seeded from public games on Lichess, which publishes its game database under the Creative Commons CC0 1.0 Universal Public Domain Dedication. Lichess does not require attribution; we credit them gratefully. We index only cleared public figures (titled players) as searchable names; other players' games appear but are not a search key, and we honour removal requests at brightmoves648 at gmail.com. Bright Moves is not affiliated with or endorsed by Lichess.

Other open-source dependencies

Bright Moves is built with Next.js, React, TypeScript, and dozens of additional open-source libraries. The full list of direct dependencies and their licenses is available in our public package.json. Each is used under the terms of its respective license.

Bright Moves is committed to honouring the licenses of the open-source software it depends on. If you believe we've missed an attribution or are out of compliance with a license, please contact us at legal at algebrics.com.

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