As far as I can see Tarver is applying the US copyright concept of derivative in the license and that means that it would be hard to show that a non-compliant v

As far as I can see Tarver is applying the US copyright concept of derivative in the license and that means that it would be hard to show that a non-compliant version of Shen was not derivative. You'd have to use clean-room techniques and show that the code you produced wasn't lifted from the sources given. And in addition you would probably get nil support from the people running the project so I'd say the license works pretty well to stop forks. Whether it should stop forks, you can argue, but as a tank-trap its pretty good. "Do similar but incompatible implementations really typically come from a common base?" In this instance without the license the answer would certainly be 'yes'. Forking from the existing sources would be the obvious and easy route. "If a group of people have the determination to change Shen's semantics and wish to distribute it and maintain it, and people wish to use that, should they be denied? Why should anyone trust the original designing committee over the course of many years, with their only recourse being to start from scratch?" Well that's a tough one. According to Stallman the answer is 'yes' because the originator has no special rights over his work. On the other hand Stallman's idea of freedom is freedom to agree with Stallman. I prefer BSD. If we imagine that this group know what they are doing then the answer might be 'yes'. However you cannot write this proviso into a license, so you have to allow the half-assed changes along with the good ones and you're back to a free for all. Pragmatically what I think is that the Shen group are very good; they are the only ones with the expertise and they have a good track record of delivery. The Shen spec looks good. I've read Tarver's book on Qi and from what I can see the whole semantics of the language is mixed in with a bunch of proofs in math'l logic that I for one wouldn't want to mess with. If they drop the ball, we should step in, but If you did have a case for changing the spec, my money would be that the best thing to do is to approach the group and put forward your case. I'll say one thing for Tarver and what he does; it sure is different. Fifteen years on, with billions of free hours, open source has failed to deliver a popular Linux desktop. Maybe we should start being a little open minded about methodologies and licenses before jumping on people's heads. The important thing is to deliver.