The only "problem" I see with the gpl is that when ace is gpl'd every addon that uses ace also has to be licensed under the gpl... Changing the license of a widely used library might result in unforseen problems .9
I guess a solution would be a new major revision which is licensed under the gpl .. so current addons are not affected by the change I guess.
I think the current situation with Ace is that every author that contributed a patch has the right on his code... so changing or attaching a license need the allowance of everybody that added a line to ace .. or it would have to get rewritten :)
I wonder if the GPL would allow us to still use our addons with the wow client :O) Maybe we would need the LGPL instead.
I like creative commons licenses because they are much more easy to read and are translated to many languages. When I follow the news around gpl2 vs gpl3 this is making me sick.