Effective 13 October 2026
Licence
Blunderbook is licensed to you under the GNU General Public License, version 3 or later (“GPLv3”). A copy is included in the app. Your rights to use, copy, modify and redistribute the app are those GPLv3 grants, and these terms do not limit them. In particular:
- You may use the app on any number of devices.
- You may obtain the complete corresponding source code, modify it, and redistribute your modified version under the same licence.
- No term of this agreement, and no term of any agreement applied by the distribution platform, restricts the rights GPLv3 grants you. Where any such term conflicts with GPLv3, GPLv3 prevails and the conflicting term does not apply.
Source code
The complete corresponding source for each released build is published as described on the source code page. If you cannot obtain it there, email somelchenko.work@gmail.com and it will be provided.
Third-party components
The app includes Stockfish, copyright 2004–2026 The Stockfish developers, licensed under GPLv3, and its neural network, also under GPLv3. The chess pieces are the cburnett set by Colin M.L. Burnett, licensed under GPL version 2 or later and used here under version 3. Opening names come from the Lichess chess-openings data set, which is in the public domain. All of them are listed with their sources in the app’s About screen and in the published source.
Premium subscription
Analysing your games is free. An optional monthly subscription, Premium, adds the features listed on the app’s Plan screen at the time of purchase, such as the Mistakes tab, the deepest review depths and more tracked players. Saved reviews stay readable whether or not you subscribe.
Premium is billed through your Apple Account and renews monthly at the price shown by the App Store until you cancel. It renews automatically unless you cancel at least 24 hours before the end of the current period. Where a free trial is offered, it becomes the paid plan at its end unless you cancel at least 24 hours before. You can manage or cancel the subscription in your Apple Account settings. Refunds are handled by Apple under its own terms.
Because the app is free software, nothing in GPLv3 stops anyone from building and distributing a version without the subscription check. The subscription supports development; it does not restrict the software.
Chess.com and Lichess
The app reads publicly available game data from Chess.com’s Published-Data API and the Lichess API. It is an independent work and is not affiliated with, endorsed by, or sponsored by Chess.com or Lichess. Their services, and any changes to them, are outside our control.
No warranty
As stated in sections 15 and 16 of GPLv3, the app is provided without any warranty, to the extent permitted by applicable law. You bear the entire risk as to its quality and performance. Engine evaluations are an aid to study, not a statement of fact about any game or player. Nothing in these terms limits rights you have under consumer law that cannot be excluded.
Apple’s required terms
Apple Inc. is not a party to this agreement. Apple has no obligation to furnish any maintenance or support for the app, and no warranty obligation of any kind with respect to it. Apple is not responsible for addressing any claim relating to the app, including product liability claims, any claim that the app fails to conform to a legal or regulatory requirement, or any claim arising under consumer protection or similar legislation. Apple and its subsidiaries are third-party beneficiaries of this agreement and may enforce its terms against you as they relate to your use of the app.
Privacy
How the app handles your data is described in the privacy policy.
Contact
For questions about these terms, email somelchenko.work@gmail.com.
Changes
We may update these terms when the app, the subscription, or legal requirements change. The effective date above identifies the current version.