There is not anything that says this, that's just the way I believe it should be, for many reasons. Put simply, I don't think anyone has the right or the ability to keep complete control over something as large and important as Harry Potter.
Perhaps I can't ERASE software, but are you saying I can't stop IMPROVING it just because it becomes big?
Never. My claim is that you shouldn't be able to stop others from improving on it. I know definitions of "improve" are going to vary across the board, but the Encylopedia example is something that is an obvious improvement. What if Linus didn't want anyone else to improve on Linux?