Copyright and licences
What GreyChess owns, what others made, and the licences it uses their work under.
GreyChess
GreyChess’s software, website and design, its name and logo, and the lessons, studies, pictures and sounds made for it are © 2026 GreyChess. All rights reserved, apart from the work of others named below. You may use them as the terms of use allow.
Books, pictures and games you open in GreyChess stay yours, and so do your notes. The moves of a game, and a position, belong to no one.
Report a copyright problem
If you think something on GreyChess uses your work without the right to, write to support@greychess.com with the work, where it appears on GreyChess and how to reach you. We look into every report and remove material where it is needed.
Stockfish
GreyChess’s analysis engine is Stockfish 18, free software under the GNU General Public License version 3. It runs unmodified, as a separate program.
Pieces
Papercut pieces by Nikolay Anzarov and Totoy pieces by Kosal Sen, under CC BY 4.0.
Lessons and studies
Some lessons and studies use material shared under a licence that asks for a credit:
- DeepMind, ChessBench from "Amortized Planning with Large-Scale Transformers: A Case Study on Chess" (Ruoss et al., NeurIPS 2024), github.com/google-deepmind/searchless_chess, CC BY 4.0. Positions selected and moves shortened by GreyChess. Source
- Ana Schaigorodsky, "Chess Database", figshare, doi.org/10.6084/m9.figshare.4276523.v1, CC BY 4.0. Games selected and headers shortened by GreyChess. Source
Everything else
The licences of the other software, fonts and pieces in GreyChess are in licences.txt.