I've read below and I see where you've changed your thinking. That said, I've seen many people (not necessarily on HN) espousing the belief that once the copyright holder releases, they're now legally committed to releasing all their future changes as well.
In a lot of GPL projects, this is essentially the case, because they either do not have copyright assignation, and have lots of external contributors (Linux, for example) or do have copyright assignation, but to a non-profit dedicated to the principles of the GPL (FSF stuff). People tend to forget about the third case, where a company has copyright assignation for contributors (Oracle stuff), or doesn't take contributions (common in dual commercial/GPL stuff).
Where does this line of thinking originate?