Credits & Third-Party Notices

XRP CHESS is built on open-source software. This page lists every third-party component we use and the license it’s under, including the GPL-licensed Stockfish chess engine that powers our “Vs Stockfish” mode.

# Credits & Third-Party Notices

XRP CHESS is built on top of a stack of open-source libraries and one
GPL-licensed component (Stockfish). This file lists every dependency
that requires attribution under its license, plus the chess engine
that requires source-code availability under the GPL.

If you need the verbatim license text for any of these, run
`npm view <package-name> license` or visit the package's homepage.

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## Special — Stockfish (GPLv3)

The chess engine that powers our "Vs Stockfish" mode is **Stockfish**,
a strong free chess engine licensed under the **GNU General Public
License v3.0 or later**.

- **Project:** https://stockfishchess.org
- **Source:** https://github.com/official-stockfish/Stockfish
- **License:** GPLv3+ — see `LICENSES/STOCKFISH.txt` in this repo
- **Bundled artifact:** `public/stockfish/stockfish.js` and
  `public/stockfish/stockfish.wasm`

Per GPLv3 §6, the corresponding source for the Stockfish binary we
ship is publicly available at the GitHub link above. We have not
modified the engine; the upstream tag we use is referenced in
`package.json` (`"stockfish": "^18.0.7"`).

Stockfish is © its contributors and is **not** covered by the
proprietary license that governs the rest of this repository.

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## Runtime dependencies (npm)

| Package | License | Project |
|---|---|---|
| next | MIT | https://nextjs.org |
| react / react-dom | MIT | https://react.dev |
| next-auth | ISC | https://next-auth.js.org |
| @auth/mongodb-adapter | ISC | https://authjs.dev |
| mongoose | MIT | https://mongoosejs.com |
| mongodb (driver) | Apache-2.0 | https://www.mongodb.com |
| chess.js | BSD-2-Clause | https://github.com/jhlywa/chess.js |
| stockfish (npm wrapper) | GPL-3.0 | https://github.com/nmrugg/stockfish.js |
| socket.io / socket.io-client | MIT | https://socket.io |
| zod | MIT | https://zod.dev |
| zustand | MIT | https://github.com/pmndrs/zustand |
| @tanstack/react-query | MIT | https://tanstack.com/query |
| framer-motion | MIT | https://www.framer.com/motion |
| matter-js | MIT | https://brm.io/matter-js |
| lucide-react | ISC | https://lucide.dev |
| tailwind-merge | MIT | https://github.com/dcastil/tailwind-merge |
| class-variance-authority | Apache-2.0 | https://cva.style |
| clsx | MIT | https://github.com/lukeed/clsx |
| @radix-ui/* | MIT | https://www.radix-ui.com |
| pino / pino-pretty | MIT | https://getpino.io |

## Build / dev dependencies

| Package | License |
|---|---|
| typescript | Apache-2.0 |
| tailwindcss | MIT |
| postcss / autoprefixer | MIT |
| eslint / eslint-config-next | MIT |
| vitest / @vitest/ui | MIT |
| @playwright/test | Apache-2.0 |

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## Icons

Icon glyphs are from **Lucide** (ISC license). Lucide is a fork of
Feather Icons (MIT). Both retain their original licenses.

---

## Fonts

If/when self-hosted webfonts are added, list them here with their
license (Google Fonts metadata, OFL, etc.).

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## Assets

- **NFT pieces** (`public/nft-skins/`, `public/nft-gallery/`) — XRP CHESS
  original artwork. © 2024-2026 XRP CHESS.
- **Boards** (`public/test-chessboards/`) — sourced and licensed for
  XRP CHESS use. See internal asset register for provenance.
- **Pawn sprites** (`public/marching-pawns/`, `public/pieces/`) — XRP
  CHESS originals.

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## Reporting a missing credit

If you spot something we should have credited and didn't, please open
an issue on the project's bug-report form (`/contact` on the live
site) and we'll add it within one business day.