Interesting. Do you have details on which jurisdictions do not allow this, and why?

I admit that I'm not familiar with international copyright law. I do know that several GNU projects, and other high profile open source projects, have a policy in place wherein contributors have to agree to a copyright assignment agreement before they can contribute their modifications.

If that's not possible in some regions, they clearly still have some means of continuing to uphold their own IP. I suspect it's not as harsh as completely avoiding contributions from some regions of the world. Unless I'm mistaken.