Odd -- I thought this was a private discussion until now... I'm replacing a bit of the context to allow others to see it fully. Hope that's OK.
Alex Hudson home@alexhudson.com writes:
An obvious example is the Perl GPL/Artistic thing (as mentioned above), but I would bet that a lot of people do dual-license with the GPL - i.e., this is Free if what you're doing is Free, otherwise you pay me $$$.
Me:
You can't restrict GPL'd software like that. It is either GPL or it isn't: adding restrictions violates FSF's copyright on it.
Alex:
You certainly can :) The FSF doesn't automatically have copyright over GPL software. A lot of people *give* copyright to the FSF, for either legal or practical reasons.
Me:
No, but they have copyright over the GPL, which prevents anything other than "Fair Use" of it in another licence:-
Alex:
That's nothing to do with dual-licencing issues, though. Dual licensing doesn't alter the terms of either license, it only specifies the terms in which you may accept to be bound by the license.
Isn't it? Can you dual-license and deny them the option of taking the GPL option? Even if you can, they can surely be passed it by someone who is eligible for a GPL licence under you definition, who would only be able to pass it on as pure GPL unless you're violating its FSF copyright.
(PS: In English, to license - verb; licence - noun. I think.)