> To put it another way, once you license something under
> GPL, it is forever GPL.
It's forever GPL for people who use it under the GPL license. If you're the copyright holder, not a licensee, you can change the license if you want to. Of course that doesn't stop people from using existing GPL copies, and you do have to be the actual copyright holder (e.g. if you accepted patches from other parties, you have to get permission from their authors to make such a change). But given such permission, a change can totally be made.
An example is the Mozilla code, which used to be licensed under a tri-license that included the GPL and was relicensed to a different license (MPL2). This process required finding everyone who had copyright on the codebase (several companies and a number of individuals) and getting their permission for the license change.
Now it's true that using the BSD license means you don't have to hunt down those other contributors and get their permission to relicense, so the bar for the author taking the code proprietary is lower (and in fact identical to the bar for anyone else doing so).
I don't understand why Mozilla would need extra permissions to upgrade from the old tri-license to MPLv2?
The MPLv1 already had an auto-upgrade clause that allowed any downstream to use and distribute the code under a later version published by the license steward; the MPLv2 also is implicitly a triple-license with LGPL/GPL.
MPL v1.1 "6.2. Effect of New Versions" does mention the new version of the license has to be published by Netscape instead of the Mozilla Foundation; was that the issue perhaps?
This page seems to agree with my reasoning in "Does Mozilla need permission from anyone to change the MPL?"
"No permission is needed from any contributor to upgrade the codebase from MPL 1.1 to MPL 2 because the MPL 1.1 contains within itself a provision which allows software under 1.1 to be redistributed under a later version of the licence."
It's forever GPL for people who use it under the GPL license. If you're the copyright holder, not a licensee, you can change the license if you want to. Of course that doesn't stop people from using existing GPL copies, and you do have to be the actual copyright holder (e.g. if you accepted patches from other parties, you have to get permission from their authors to make such a change). But given such permission, a change can totally be made.
An example is the Mozilla code, which used to be licensed under a tri-license that included the GPL and was relicensed to a different license (MPL2). This process required finding everyone who had copyright on the codebase (several companies and a number of individuals) and getting their permission for the license change.
Now it's true that using the BSD license means you don't have to hunt down those other contributors and get their permission to relicense, so the bar for the author taking the code proprietary is lower (and in fact identical to the bar for anyone else doing so).