Annoyance du jour (and I want to stress that this isn't in response to any of the posters in this thread) is when people authoritatively make statements regarding something they don't understand.
In this particular case, someone has informed me that I, an end user, do not have the right to modify open source software as I see fit. Apparently I'm allowed to look, and I'm allowed to commit changes back to the "official" publisher, but I can't actually use the modified version unless the publisher approves it and releases a new version with my changes.
This is not a discussion of a specific piece of software with its own "custom" licence, but is rather a statement that apparently applies to open source software as a whole. I'm not even going to bother trying to reply to that nonsense.