you don't have to own all the rights to license the software, you just have to own the rights and not have assigned them.
That is why back in 200? TPL licensed to INTC while PTSC licensed to AMD.
TPL had the rights of Chuck Moore while PTSC had the right origionally owned by Russel Fish.
So any "owner/inventor" can legally assign rights without permission from the other O's/I's unless said O/I is contractually precluded from such action.