Eelco de Groot wrote:Fair enough Harm. But that also means there is very little means for Vas himself to protect his copyright against rewriting, even if he had never taken a look at Crafty's sources or Fruit sources.
Indeed, copyrights (and thus GPL, which is merely tying up a few details copyright law leave open) provide a very meagre protection. Basically only against hex-edit jobs, simple disassembly / decompilation or copy-paste of sources. Not against rewrite. Patents offer more protection, but also more restrictions on what can be patented. (You could never patent a whole Chess engine, as it contains for 99% stuff that is common knowledge, and the 1% that makes it unique might be dispersed through the code and not easily identifiable. But a specific pruning trick like null-move would IMO indeed have been patentable.) But that s of course too costly to make it worth it, especially since you would have to do it in every country separately. So your only legal protection is basically just making it technically difficult: encrypting or obfuscating the code.
That is what Vas has stated himself, and why he just seems to shrug it all off as not pertinent to his business. Neither has Fabien much ground for any claim of infringement of his own copyright, even if he had never tried to protect it by means of the GPL. As I understood it Fabien actually relinquished all his rights to Fruit anyway and these now rest with the FSF. So legally, Fabien's open letter changes nothing in my opinion as he has relinquished at least the GPL, even though the original copyright might still be his, I would not know how this is legally read.
I think that the FSF is much more likely to take legal recourse as Fabien would be. It is why they exist, while for Fabien it would be an extremely costly hobby with virtually nothing to gain. But of course I agree that Fabien's opinion on this has no added value and his letter changes nothing: Both Strelka and Fruit are open source, and we do not need Fabien spot the similarities or differences. It would have been important at the time when Strelka was still closed source, as it was when it was shown to Fabien.
So this discussion is in the end not about copyright, but about honour, fair use of ideas, and recognition. Which are important enough of course, but inherently less objective to judge as they are guided by unwritten law.
Sure, but those are very subjective matters. There are enough people that would see absolutely nothing wrong / dishonest / shameful with rewriting an open-source code, and use it as a starting point for an improved engine. In fact I am pretty sure that more than 75% of all engines we know are exactly that.