Acknowledgements

Knightcap’s own code is proprietary. The app includes or uses the following third-party works. This file is bundled in the app and shown under Settings › About › Acknowledgements.

Chess pieces — Poly Haven “Chess Set”

• Author: Riley Queen, published by Poly Haven (2023)
• Source: https://polyhaven.com/a/chess_set
• License: CC0 1.0 (public domain dedication). Poly Haven: “Our assets are all licensed as CC0”; no attribution required (https://polyhaven.com/license). Credited here anyway.
• Modifications: Only the geometry is used; the king’s cross is enlarged. Knightcap renders the pieces with its own materials, lighting, outline and shadows (art/pieces3d/render.py, Blender) into 2D sprites.
• Files: model in art/pieces3d/source/; sprites in ios/ChessPuzzles/Resources/Assets.xcassets/Pieces3D/

ChessKit

• Source: https://github.com/chesskit-app/chesskit-swift (version 0.17.0)
• License: MIT (full text below)

cozy-chess

• Source: https://github.com/analog-hors/cozy-chess (crate cozy-chess 0.3.4, pinned in engine/Cargo.lock)
• License: MIT, Copyright (c) 2021 analog-hors (same terms as the MIT text below)
• Use: move generation inside Knightcap’s goal judge (engine/judge), which ships in the app as KnightcapJudge.xcframework and runs in the puzzle pipeline.

Chess puzzles

• Source: Lichess puzzle database, https://database.lichess.org/
• License: Creative Commons CC0 1.0 (public domain). Every puzzle is re-verified by Knightcap’s own pipeline before publishing.

Google Mobile Ads SDK and User Messaging Platform

• Source: https://github.com/googleads/swift-package-manager-google-mobile-ads, https://github.com/googleads/swift-package-manager-google-user-messaging-platform
• License: Google Mobile Ads SDK terms, https://developers.google.com/admob/terms. Used for ads in the free tier only; never started for Premium users.

Sound effects

Original sounds created for Knightcap (scripts/make-sounds.py). No third-party audio.

Mascot

The sleepy knight mascot (ios/Shared/Mascot.xcassets) is cut from Knightcap’s own app icon (scripts/make-mascot-cutout.py). No third-party art.

Server-side only (not distributed in the app)

Stockfish 19 (official sf_19 binary, pipeline deep check) and python-chess (GPL-3.0) run only in the puzzle pipeline on Knightcap’s servers and are not part of the app.

Planned, not yet bundled

No analysis engine is bundled yet. The in-app game analysis engine is undecided; research favors Arasan v26.1 (MIT code, with its LICENSE covering the network directory), with Patricia 5.1 (MIT) as the fallback (specs/005-goal-based-puzzles/research.md R2). Viridithas v20 was evaluated and not chosen (no MultiPV). Whichever engine ships is recorded here with its pinned version, net hash and license texts.

MIT License (ChessKit)

MIT License

Copyright (c) 2023 ChessKit (https://github.com/chesskit-app)

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.