More than a year ago, the open source chess engine Stockfish announced that they had filed a lawsuit against the chess software company ChessBase.

According to reports, Stockfish, with the support of German copyright lawyers and the broad support of the development community, filed a lawsuit against ChessBase in the Munich court, requiring the other party to enforce the termination clause of the GPLv3 license, claiming that ChessBase’s products Fat Fritz 2 and Houdini 6 have repeatedly Violates the terms of the GPL license.

Fat Fritz 2 and Houdini 6 are based on Stockfish development. According to GPLv3, the sale of modified copies of ChessBase is permitted provided that the corresponding modified source code and all information required to build the program are provided. However, ChessBase used Stockfish’s code almost unchanged, not only did not credit the source, but claimed its originality, but also did not abide by the GPL license – their customers did not receive the GPL license text covering these programs and the corresponding source code for these programs.

Recently, Stockfish announced that they have reached an agreement with ChessBase (German and English PDF), this agreement strengthens the Stockfish project’s goal of providing the world’s first open source chess engine as free software, and allows ChessBase to continue to distribute this software in the future.

Stockfish has reinstated the ChessBase distribution license, which they believe is in the spirit of free software and beneficial to the community. ChessBase has also recognized the value and potential of open source software, Stockfish in particular, and made a clear commitment to respect the principles of free software.To prevent future violations, ChessBase will create the position of a Free Software Compliance Officer and will maintain a domain at [foss.chessbase.com] website listing their products using Free and Open Source Software (FOSS).

Additionally, ChessBase stated that the neural networks they provide for use with Stockfish will be open sourced under the GPL or a compatible license.

Finally, the Stockfish team calls themselves “power for love” amateurs who prefer to write code rather than litigate, so they are not asking for damages or other forms of financial compensation.

further reading