Shriramana Sharma wrote: > Say a person X writes a library libfoo. He licenses the library out > under both the GPL and a commercial licence. I think you mean "and a proprietary license". > A person Y uses libfoo under the GPL. He goes and does a lot of > improvements in the library since it is under the GPL. Now the modified > version of libfoo is copyrighted by both X and Y. Assuming Y's improvements involved sufficient creativity to make them copyrightable, yes. In the absence of strong evidence to the contrary, you should assume they do. > So X would not be able to import such improvements into the main > distribution of libfoo since then he would not be able to dual-licence > it - specifically he would not be able to licence it commercially, not > owning it entirely. He must either take Y into his business or obtain a > waiver from Y by one-time payment or whatever. Again, you mean "proprietary", not "commercial". X already has Y's permission to sell the software commercially, as long as X does so under the GPL. X just may not apply a proprietary license to the software without permission from Y. > My question is: What would be considered a big enough > difference/modification that X would need Y's permission for backporting > the changes? Anything sufficiently creative for copyright to exist in it. You assume above that Y does hold copyright in the modified version, and if that holds true, X would need Y's permission. For the specific cases you gave, I agree with Andrew Donnellan's assessments. - Josh Triplett
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