andrejcher wrote:To SF team: what is your decision?
I've been slow to reply, because I think it is a very difficult question. I really don't know what to think, and I feel quite uncomfortable about the situation.
In principle, I fully share Miguel's view. There is little point in using a GPL license if we arbitrarily grant exceptions to the license to everybody who asks politely. I also share Joona's concern that we will see a growing list of proprietary Stockfish derivatives and requests for exceptions to the license, and that just replying to the requests and reviewing the code of everything will get a nightmare. The two projects mentioned in this thread won't be the last ones. It is possible to make lots of money from selling chess programs for iOS (and no doubt Android as well), and programmers are only just beginning to discover this.
On the other hand, it doesn't feel right to punish those who are honest and actually ask, rather than just using the code illegally (which will almost certainly happen sooner or later, and may already have happened). If we're too restrictive in what we allow, there is a risk that more people use the illegal approach.
I also think of those who try to bring their own, completely original programs to iOS or Android. As Andriy pointed out himself previously in this thread, writing a chess engine from scratch takes a considerable amount of work. By using Stockfish as the starting point, someone working on an iOS chess app gets a huge competitive advantage for free compared to someone who starts from scratch. And this competitive advantage may matter a lot, because there is potentially a significant amount of money to earn. I fear that the free iOS Stockfish is already hurting the sales of commercial programs somewhat, and this problem will obviously get worse with a growing number of Stockfish-derivatives. The question, therefore, is the following: Is having to publish your source code under the GPL really an unreasonably high price to pay for this competitive advantage? After all, you can still charge for your program, and because there is no easy way for ordinary users to install it other than buying it from the App Store anyway, the public availability of the source code shouldn't hurt the sales much, if at all.
At the moment, although I see strong arguments both for and against, I lean mostly towards not allowing such exceptions to Stockfish's GPL. But I am still very much in doubt, and depending on how the current discussion develops, I may still change my mind.