Licenses & credits

# Third-Party Notices ChessGrains is an independent project; it is not affiliated with or endorsed by Lichess, the Stockfish team, or SuperMemo World. This file lists third-party software and data used by ChessGrains, with their licenses and sources. It is intended to be the source of truth rendered by any future in-app Licenses page. --- ## Engines and analysis ### Stockfish (GPLv3) - **What:** The Stockfish chess engine, compiled to WebAssembly by [nmrugg / stockfish.js](https://github.com/nmrugg/stockfish.js) from the upstream [official-stockfish/Stockfish](https://github.com/official-stockfish/Stockfish) source. - **Files:** `public/stockfish.js` (and `public/stockfish.wasm` at runtime). - **License:** GNU General Public License, version 3 (GPLv3). - **Full license text:** see `public/LICENSE-stockfish.txt` in this repository (served at `/LICENSE-stockfish.txt`). - **Upstream source:** - nmrugg port: <https://github.com/nmrugg/stockfish.js> - official-stockfish: <https://github.com/official-stockfish/Stockfish> - **How we use it:** The engine runs entirely in the user's browser, inside a dedicated Web Worker spawned via `new Worker('/stockfish.js')`. The ChessGrains application communicates with the engine only through UCI text messages (`postMessage`). No Stockfish source code is linked into the ChessGrains application bundle. **GPLv3 source / corresponding offer (§6):** The WebAssembly engine files (`public/stockfish.js`, `public/stockfish.wasm`) are built from the [nmrugg/stockfish.js](https://github.com/nmrugg/stockfish.js) project, which in turn tracks [official-stockfish/Stockfish](https://github.com/official-stockfish/Stockfish). You may obtain corresponding source from those repositories (and matching release tags for the binaries you ship). The full GPLv3 text shipped with the app is at `/LICENSE-stockfish.txt`. For source requests tied to a specific public build of ChessGrains, contact the operator at **[hello@chessgrains.com](mailto:hello@chessgrains.com)**. --- ## Data ### Lichess puzzle database (CC0) - **What:** [lichess.org puzzle database](https://database.lichess.org/#puzzles). - **License:** CC0 1.0 Universal (public domain dedication). - **How we use it:** Puzzle rows (FEN, solution moves, themes, rating) are imported into the ChessGrains database via `scripts/import_lichess.js`. ### Lichess public API - **What:** Per-user game archive endpoint (`lichess.org/api/games/user/…`) and rating-history endpoint. - **Governing terms:** the [Lichess Terms of Service](https://lichess.org/terms-of-service) and the [Lichess API policy](https://lichess.org/api). - **How we use it:** On demand, for users who have linked their Lichess username to their ChessGrains profile, to analyse their own games. Requests are sent with a descriptive `User-Agent` identifying ChessGrains. --- ## Libraries (application code) These libraries are bundled into the ChessGrains application at build time. Each is used under its own permissive license; the relevant license text is installed into `node_modules/<package>/LICENSE` by the package manager and redistributed with the built application. | Package | Version | License | Link | | -------------------- | ------- | --------- | -------------------------------------------------------- | | Next.js | 16.x | MIT | <https://github.com/vercel/next.js> | | React / React DOM | 19.x | MIT | <https://react.dev> | | chess.js | 1.x | BSD-2 | <https://github.com/jhlywa/chess.js> | | react-chessboard | 4.7.x | MIT | <https://github.com/Clariity/react-chessboard> | | Tailwind CSS | 4.x | MIT | <https://tailwindcss.com> | | Supabase JS SDK | 2.x | MIT | <https://github.com/supabase/supabase-js> | | Supabase SSR helpers | 0.x | MIT | <https://github.com/supabase/auth-helpers> | | pg (node-postgres) | 8.x | MIT | <https://github.com/brianc/node-postgres> | | csv-parser | 3.x | MIT | <https://github.com/mafintosh/csv-parser> | | fzstd | 0.x | MIT | <https://github.com/101arrowz/fzstd> | | node-fetch | 3.x | MIT | <https://github.com/node-fetch/node-fetch> | | dotenv | 17.x | BSD-2 | <https://github.com/motdotla/dotenv> | ### react-chessboard (MIT) ChessGrains renders interactive boards with [react-chessboard](https://github.com/Clariity/react-chessboard) (MIT License). Copyright (c) 2022 Ryan Gregory Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. --- ## Algorithms ### SuperMemo-2 (SM-2) spaced-repetition algorithm - **What:** ChessGrains implements a spaced-repetition scheduler inspired by the SuperMemo-2 (SM-2) algorithm originally described by Piotr Woźniak (SuperMemo World) in 1987. - **ChessGrains implementation:** `src/lib/srs.ts` is an original TypeScript implementation written for ChessGrains. It is distributed under the same license as the rest of the ChessGrains application source. - **SuperMemo World policy:** SM-2 may be used in other software without a separate license fee when the following attribution is included prominently (see also the [SuperMemo licensing notes](https://www.supermemo.com/en/blog/licensing-and-copyrighting-of-supermemo-algorithms)): > **Algorithm SM-2, (C) Copyright SuperMemo World, 1991.** > > - <https://www.supermemo.com> > - <https://www.supermemo.eu> ChessGrains is not affiliated with or endorsed by SuperMemo World. Later SuperMemo algorithms (SM-15, SM-17, etc.) are proprietary to SuperMemo World and are not used in this application. --- ## Copyright Copyright © 2026 ChessGrains. All rights reserved. The ChessGrains application source (everything in this repository outside `public/stockfish.*` and `node_modules/`) is proprietary. The third-party components listed above (Stockfish, react-chessboard, the Lichess puzzle database, SuperMemo SM-2 attribution, and the bundled npm packages) retain their respective licenses as documented in each section. For licensing inquiries: [hello@chessgrains.com](mailto:hello@chessgrains.com).