I'm not sure I follow you.
Yes, if my work is covered by *GPL, you can ALWAYS use it if you follow the conditions in the license.
However if you for some reason can't or won't, you can ask me for a relicense. If you don't I can sue you for violating the *GPL. If you do, you have to follow the conditions of the new license otherwise I can sue you.
Of course, if you later decide that oh well following the *GPL is not that bad in comparison after all, it is possible and even probably that I can't sue you for breaking the relicense as long as you follow the *GPL.
The point it that you must show that you follow either *GPL or my relicense in order to not be a copyright infringer. You don't have to follow both though.
Patrik Stridvall wrote:
yes, even if it contradicts your relicense. If you "work on" an *GPLed product, what you do is automatically claimed by *GPL, thus you can't make any license on your work that is *GPL free.
and if your are relying on your copyright protection to allow you to benefit on the relicense, you don't have it in this case. Remember also that the *GPL is pretty much irrelevent so long as you are not distributing to the public, so it's not a great cost to choose to go that route.
It's a little different, because I think the burden of proof is different. Pending on the what you have in your relicense, it's easy to show that the receiver is covered because they have the software. On a GPL violation, you have to show that what they are doing with the software is in violation of the license - which might be much harder to show.
-r