As far as I understand it, GPL also offers the ability to reabsorb changes made to forks in the package, so if someone forks off Ace, and makes some nice improvements to it, we can then merge them into the trunk.
Ah, yeah, that'd be the benefit of GPL over BSD in this case, I suppose. Although to be strictly accurate, this assumes that someone:
- Forks a BSD licensed addon,
- makes significant and non-trivial improvements to it,
- releases it using a more restrictive (ie, non-free) license,
- AND the improvements are good enough that the maintainer of the original addon wants to backport them.
Seems unlikely, but it could happen. :D
On the other hand, as I understand the GPL, I believe dafire is correct that if Ace (or a library, like TouristLib or whatever) is GPLed, then all Ace addons (or addons that use the library) would have the be GPLed too. While that might be nice in theory, the logistical difficulties seem...daunting. I believe the LGPL would avoid this whole mess, and might be a better choice as a result.
Edit: And that's not even touching on Malreth's disturbingly plausible argument below. :)