The kind of arguments you raise here have always, to me, basically looked like:

"I want something for nothing"

Or in more detail:

"I want to take something you created and agreed to share with me (on the proviso I like-wise share any changes as an exchange of value). I deem your software valuable to me but I won't be paying you money for it. I'll add something else to it so it fits my use-case. But, I refuse/object to sharing my changes because they're valuable."