Alright, I am in the process of changing my mind, not there yet, but I now find it more likely that Rybka started its life as Fruit thanks to the contributions of Zach and BB. Having said that I am interested to have a discussion about the sense and nonsense of GPL.BB+ wrote: this copying appears to go beyond what is (or has been) acceptable in the field of computer chess/games [and I strongly feel that this is the proper standard to use for "originality", as opposed to a "legalistic" one, where perhaps only "code" is considered], and I personally find the attempts to dismiss this all as happenstance (or "unimportant") to be a bit outré. That being said, there is also a tendency to exaggerate the Rybka/Fruit connection in some other circles. [And by now, I think Rybka 4 has almost zero connection to the Fruit origins].
Sense: I sympathize with the sentiment to share in order to make progress, usually the more people, the more progress as everybody has their own set of unique idea's.
Nonsense: the stipulations of GPL are a piece of mud. They incite to entrapment or incitement, I don't know the right English juridical term. Big chance a judge will trash GPL as entrapment. It may go like this in a court room:
Judge - Mister X, what have you done to protect your work?
X - I released my code under GPL.
Judge - Is that all?
X - Yes, your honor.
Judge - do you also leave your car, house unlocked?
X - No, your honor.
Judge - Why then your code?
X - I don't know sir.
Judge - If you leave your car unlocked and it's stolen because of that do you think the assurance company will pay?
X - no sir.
Judge - I will tell you my verdict. Mister X, you are behaving like a bank that stores all its money on the street, puts a sign on it with the text: forbidden to steal and then you come into my court room to complain that all is stolen. That is entrapment Mister X. You have an obligation to protect. Now get out my court room as soon as possible at your own chosen speed.
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I have looked at the internet for GPL lawsuits and found no case of a verdict, only settlements. Perhaps I should look deeper.
Remains the issue of moral. And actually I find the concept of Reverse Engineering (RE) and then calling it your own a lot more corrupt then taking something that is said free (but hey!, don't use it as your own) and use it as a base to make something of your own by tons of changes, even fundamental ones (mail-box to bit-board).
I think this Rybka=Fruit issue got too much attention. Reason: sloppy GPL stipulations.
I can imagine that people with a scientific / university background will differ as they are raised in the opinion and conviction that everything should be free and should be shared for progress reasons but then PLEASE don't add such silly stipulations as an obligation to release the source code of something that is far beyond the original work.
Ed