On July 4th this yr, after a number of ready, Stockfish and Chessbase lastly acquired their first day in courtroom. The battle between the 2 software program makers started when ChessBase launched a chess engine known as “Fats Fritz 2” that was allegedly a repackaged model of Stockfish. This led to some important recrimination, together with on this very web site. The case was of curiosity to free software program advocates and chess gamers in every single place, so we despatched a Lichess developer to the courtroom in Munich to witness occasions firsthand and report on them. We additionally spoke with ChessBase CEO Matthias Wüllenweber. (Full textual content of the interview)

The character of this dispute may be troublesome to clarify to those who should not aware of the Free Software program design course of. This course of not solely produced Stockfish and Lichess, however different well-liked software program like VLC, Firefox, and the Linux OS that in all probability runs the servers of all of your favourite web sites.

Not like proprietary software program, the code from free software program can be utilized freed from cost in another challenge, however you have to fulfill different non-financial necessities of the license. Within the case of the “GPLv3” license that Stockfish makes use of, which means you have to inform customers clearly that the software program they’re utilizing is free software program, and make the supply code, with any modifications you’ve made, publicly out there to make use of in the identical manner that the unique is. On this case, neither the Fats Fritz 2 code nor the license textual content was  made out there. 

Shortly after Fats Fritz 2 was launched, the Stockfish workforce despatched a stop and desist letter to ChessBase asking that they fulfill the necessities of their license for Fats Fritz 2, and, very importantly, additionally fulfill the license for another ChessBase merchandise which may comprise Stockfish code. After receiving the letter, Chessbase launched a brand new product “Fats Fritz 2 SE”, packaged with a duplicate of the GPLv3 license and a duplicate of the supply code with what seems to be a distinct, and weaker, neural web. The code for the unique Fats Fritz 2 has but to be launched.

ChessBase admits they violated the license, though by mistake, and solely briefly. In accordance with Wüllenweber: “With Stockfish we didn’t fulfill the GPLv3 necessities and frantically scrambled to repair this inside days of the primary publication. The fault that the majority aggravated me was that the unique model in some way entangled the brand new neural community in a manner with the engine that made it unusable in another context. A transparent violation. We mounted it instantly, but it surely was [in]appropriately perceived as unhealthy intention. As soon as in your life, you might have this challenge the place every little thing that may go flawed goes flawed.”

Along with the lacking authorized necessities, ChessBase additionally didn’t give Stockfish a lot public recognition for his or her contribution both. The ChessBase homepage known as Fats Fritz 2 “the brand new #1” engine.” Presumably, supplanting the now “inferior” Stockfish. Fats Fritz 2 creator Albert Silver did interviews the place he mentioned what it was prefer to “begin virtually fully from scratch.” This stuff precipitated important resentment among the many Stockfish workforce. In accordance with Wüllenweber; “Within the publication means of Fats Fritz 2, I made a number of errors. Consequently, the Stockfish authors are actually fairly offended at us, and I can totally perceive this. Probably the most severe error was to not describe the challenge to them beforehand. If they’d objected, we might have canceled it. One other error was to do overzealous boasting about Fats Fritz on our site. Whereas we believed that the brand new neural web was unique and precious, this advertising and marketing downplayed Stockfish in an unacceptable method. These articles have been naturally learn and quoted broadly, whereas no one noticed the official promoting and packaging which all the time mentioned “Based mostly on the open-source engine Stockfish” because the very first declare.

The again of the packaging of a bodily copy of Fats Fritz 2

The Stockfish workforce was equally unflattering of their communication concerning the subject. On the official Stockfish weblog Joost VandeVondele wrote: “ChessBase’s communication on Fats Fritz 2, claiming originality the place there’s none, has shocked our neighborhood. Moreover, the engine Fats Fritz 2 fails to persuade on unbiased ranking lists, casting doubt on the usefulness of these modifications. Certainly, we really feel that prospects shopping for Fats Fritz 2 get little or no added worth for cash. Claims on the contrary seem deceptive.”

The stop and desist letter wouldn’t be the tip of the authorized wrangling. Whereas some steps had been taken to convey Fats Fritz 2 into compliance, there was nonetheless an issue with one other ChessBase product. “Houdini 6” is one other older engine that ChessBase has been promoting since 2017. What was claimed to be supply code for Houdini, acquired by unclear strategies, was posted anonymously on GitHub, and it bore a placing resemblance to Stockfish code. Six weeks after the primary stop and desist letter, the Stockfish workforce ready one other for Houdini, and this one would carry a distinct demand that will change into the important thing subject within the upcoming lawsuit; GPLv3 license termination.

Any license has to have some tooth; a particular penalty for not following its necessities. The GPLv3 wouldn’t be price a lot if the one penalty for violating it was to shrug, apologize, and do the identical factor once more later. To this finish, the second Stockfish stop and desist letter didn’t demand achievement of the license necessities for Houdini, it knowledgeable ChessBase that attributable to repeated violations, their license to make use of Stockfish code had been revoked and so they should stop distributing any Stockfish derived software program completely. When ChessBase refused, the Stockfish workforce determined to implement their license termination with a lawsuit.

We requested a Lichess dev to examine the alleged Houdini code that the Stockfish workforce submitted to the German courtroom and his opinion was clear. In accordance with him: “It isn’t an entire 1-to-1 copy. He (Robert Houdart, The Houdini developer) added customized components, and modified some components, however massive and important components of the code, undoubtedly greater than 1000 strains, are plainly and clearly the identical as Stockfish code. It additionally incorporates 1-to-1 copied and really particular feedback which in components even reference Stockfish (e.g. “To compile stockfish…” within the Makefile) and Glaurung (the Stockfish predecessor)”

However, Wüllenweber insists that there’s something unique in Houdini “A few weeks in the past, I regarded on the code samples demonstrated by the plaintiffs. I assume that from Stockfish’s viewpoint they supplied the stuff that involved them most. To me it appeared clear that each packages use the identical concepts in these code snippets. Concepts of originality and worth. To me it additionally appeared clear that Houdart expressed these concepts in his personal phrases, the place his implementation was generally fairly environment friendly or no less than totally different from the Stockfish pattern.”

A code comparability between Stockfish and alleged Houdini from the Stockfish workforce’s courtroom submissions. In addition they included proof that the compiled program behaves in apply just like the commercially launched Houdini binary.

A German civil courtroom is a much more informal affair than you might count on, there aren’t any hovering Hollywood speeches, or witnesses cracking below a shrewd lawyer’s interrogation. As a substitute, the 2 events in a lawsuit meet with the choose in a quiet room to debate the case. She asks inquiries to each events, and after the assembly is over she’s going to both make a ruling or request additional proof. Though the choose on this case made no formal ruling, she did clearly state her opinion on sure particular questions. It’s additionally potential to make extremely educated guesses on her view of issues from the strains of questioning she chooses and the themes she finds essentially the most related. In accordance with our on-site reporter, the choose on this case is satisfied that Houdini comes from Stockfish and explicitly put the accountability to show in any other case on ChessBase. She additionally appeared to agree that a number of license violations passed off, and that revocation was not solely legitimate on the whole, however an affordable final result on this specific case as properly.

A German civil courtroom appears to be like extra like a classroom.

Her principal concern appears to be the precise scope of any potential revocation. A German courtroom ruling must be outlined in a manner {that a} bailiff can perceive properly sufficient to implement, and with a Stockfish codebase that’s always rising and altering this might be troublesome to do. The Stockfish workforce appeared proud of the results of the primary listening to. In accordance with VandeVondele on the Stockfish Discord: “I believe typically we’re fairly joyful about the way it went. The choose was very educated and understood our arguments and proof fairly properly. The burden of proof has been reversed for Houdini, and we perceive that termination by few copyright holders is feasible. The scope of termination is one thing that wants additional work (which variations, which code, and so on). The choice can be to settle, with phrases that we have to mirror on, and particularly additionally focus on with Tord. (Romstad, a Stockfish Developer)“

German civil courts strongly encourage the events to discover a settlement, and the choose on this case was no exception. She spoke to each events to push them in that course. Nevertheless, evidently a settlement won’t be simple to rearrange. When requested why not merely comply with now not promote Stockfish-derived software program if he regrets doing it within the first place, Wüllenweber admitted that there was some unhealthy blood on his aspect too: “Stockfish’s public response to Fats Fritz 2 was fairly painful and damage us. Perhaps we deserved some punishment. Nevertheless, now singling us out whereas opponents drive many monetization schemes primarily based on Stockfish appears like one thing one ought to stand as much as.”

The courtroom will meet once more on March twentieth, 2023 until a settlement is reached first. If a ruling is made there might be appeals afterwards. Altogether, this case might take years to resolve. Keep tuned to all the usual Lichess communication channels for updates on this case because it develops additional.