> For the complete documentation index, see [llms.txt](https://playbook.checkmate.live/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://playbook.checkmate.live/about-checkmate-live/under-the-hood/open-source-licenses.md). # Open Source Licenses **Open Source Licenses & Acknowledgments** Checkmate is built upon the shoulders of giants, utilizing a variety of open-source software that enables us to deliver a world-class chess experience. We're deeply grateful to the developers and contributors of these projects. Specifically, Checkmate utilizes: * [**JaVaFo**](http://www.rrweb.org/javafo/JaVaFo.htm)**:** A pairing engine implementing the FIDE (Dutch) System, as described in the FIDE handbook (chapter C.04.3). JaVaFo is authored and intellectually owned by Roberto Ricca, former programmer, International Arbiter and current Secretary of the FIDE Commission "Systems of Pairings and Programs" (SPPC). * [**Stockfish 16.1**](https://stockfishchess.org/)**:** A leading open-source chess engine renowned for its strong playing ability and advanced neural network-based evaluation. This enables Stockfish to assess chess positions with remarkable accuracy. **Important Note:** While Stockfish is a valuable tool for learning and analysis, its use during live games is strictly prohibited and considered a form of cheating. Our Fair Play system actively monitors for the use of Stockfish and other chess engines to maintain the integrity of our platform. **We believe in the power of open source and are committed to supporting and contributing back to the community whenever possible.** --- # Agent Instructions This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com. ## Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter: ``` GET https://playbook.checkmate.live/about-checkmate-live/under-the-hood/open-source-licenses.md?ask=&goal= ``` `ask` is the immediate question: it should be specific, self-contained, and written in natural language. `goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.