Legal

Licenses

Theory stands on other people’s work. This page lists the third-party software, typefaces and 3D models it ships or loads, and what they are licensed under.

Last reviewed 1 November 2026

Software

jQuery 2.2.4 MIT License — jquery.org/license

localForage 1.7.3 Apache License 2.0 — github.com/localForage/localForage

three.js 0.183.0 MIT License — used for the 3D board and the narration avatar — github.com/mrdoob/three.js

Bootstrap MIT License — getbootstrap.com

jQWidgets Commercial license, held by ChessBase GmbH

ASP.NET Core, .NET 10 MIT License, Microsoft — github.com/dotnet/aspnetcore

MaxMind GeoIP2 .NET API Apache License 2.0, MaxMind — reads the IP-geolocation database below — github.com/maxmind/GeoIP2-dotnet

The wider ChessBase FOSS list lives at foss.chessbase.com.

Typefaces

Merriweather SIL Open Font License 1.1, Sorkin Type

Montserrat SIL Open Font License 1.1, Julieta Ulanovsky and contributors

3D models

The coach pieces Ours — the pawn and rook avatars are generated geometry, built by a script in this repository, and carry no third-party license

The human avatar Derived from avatars/mpfb.glb in met4citizen/TalkingHead, made with MPFB and released CC0 / public domain. It is a model of nobody in particular. (The other avatars in that repository are non-commercial and are not used here.)

Images

The narration stickers The cartoon pictures that pop up on the board while a beginner narration is speaking (the hedgehog, the dragon, the brick wall…) are Fluent Emoji 3D — MIT License, Microsoft — github.com/microsoft/fluentui-emoji

The chess engine and the chess data

The engine that runs in your browser is Fritz, ChessBase’s own, compiled to WebAssembly; it is not open source. The stronger engine you can switch to is Stockfish, running on a ChessBase server — GNU General Public License v3, the Stockfish developers — stockfishchess.org. Its license text and the source of the version we run are at foss.chessbase.com.

The master games, the LiveBook statistics, the player data and the opening catalog with its names and ECO codes all come from ChessBase databases and are not open source.

The opening character profiles and the recurring plans are computed here from those games — see AI transparency for what is measured and what is generated.

IP geolocation

The site’s usage statistics name the country and the network an address belongs to, looked up in a copy of the database kept on our own server: IP Geolocation by DB-IP (“IP to Country Lite” and “IP to ASN Lite”), licensed under Creative Commons Attribution 4.0.

Something missing?

If we have used your work and failed to credit it, or credited it wrongly, tell us through the ChessBase contact page and we will fix this page.