Leading Stockfish developers have filed suit against ChessBase to enforce their license termination claiming Chessbase has “repeatedly violated central obligations of the GPLv3 license”. The court hearing in the case Tord Romstad and Stéphane Nicolet vs. ChessBase GmbH will take place on Monday, July 4th, and Stockfish calls all interested parties to attend the hearing.
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Stockfish announcement for Public Hearing:

“As announced nearly one year ago, leading Stockfish developers have filed suit against ChessBase to enforce their license termination after repeated copyright violation by ChessBase. The court hearing in the case Tord Romstad and Stéphane Nicolet vs. ChessBase GmbH will take place soon.

In recent months, we have presented to the court detailed evidence that the ChessBase products Houdini 6 and Fat Fritz 2 have copied extensive parts of the Stockfish code base authored by the plaintiffs and that ChessBase repeatedly violated central obligations of the GPLv3 license. GPLv3 requires that the user is informed of their rights, has access to the corresponding sources, and has the right to reproduce, modify and distribute GPLed programs royalty-free.

We have applied to the court to order ChessBase to cease distributing Stockfish in all forms, including Fat Fritz 2 and Houdini 6, as the GPLv3 license has been terminated permanently according to section 8, and to cover our legal expenses.

The hearing is scheduled to take place on Monday, July 4th, 2022, 11am in Munich (Germany):

Landgericht München I
Sitzungssaal 101, 1. Stock,
Lenbachplatz 7
D-80316 München

We inform interested parties that the public is permitted to attend and will update on the progress made.
The Stockfish team”

Stockfish announced the lawsuit against ChessBase nearly a year ago:

“The Stockfish project strongly believes in free and open-source software and data. Collaboration is what made this engine the strongest chess engine in the world. We license our software using the GNU General Public License, Version 3 (GPL) with the intent to guarantee all chess enthusiasts the freedom to use, share and change all versions of the program.

Unfortunately, not everybody shares this vision of openness. We have come to realize that ChessBase concealed from their customers Stockfish as the true origin of key parts of their products (see also earlier blog posts by us and the joint Lichess, Leela Chess Zero, and Stockfish teams). Indeed, few customers know they obtained a modified version of Stockfish when they paid for Fat Fritz 2 or Houdini 6 – both Stockfish derivatives – and they thus have good reason to be upset. ChessBase repeatedly violated central obligations of the GPL, which ensures that the user of the software is informed of their rights. These rights are explicit in the license and include access to the corresponding sources, and the right to reproduce, modify and distribute GPLed programs royalty-free.

In the past four months, we, supported by a certified copyright and media law attorney in Germany, went through a long process to enforce our license. Even though we had our first successes, leading to a recall of the Fat Fritz 2 DVD and the termination of the sales of Houdini 6, we were unable to finalize our dispute out of court. Due to Chessbase’s repeated license violations, leading developers of Stockfish have terminated their GPL license with ChessBase permanently. However, ChessBase is ignoring the fact that they no longer have the right to distribute Stockfish, modified or unmodified, as part of their products.

Thus, to enforce the consequences of the license termination, we have filed a lawsuit. This lawsuit is broadly supported by the team of maintainers and developers of Stockfish. We believe we have the evidence, the financial means and the determination to bring this lawsuit to a successful end. We will provide an update to this statement once significant progress has been made.

We would like to thank our fans for their support, and encourage them to download and use the official version of Stockfish that we enjoy developing and sharing freely.

The Stockfish team“