It's common for open source projects to change licenses. To be honest, I'm pretty sure that most projects have set the bar much higher than it legally is. In other words, I think de Raadt's fantasy isn't going to happen, and if it did, the fallout would likely be that many projects would lose the ability to enforce their licenses.

Usually, when a project changes its license, it either tries to get permission from each contributor; or it makes an announcement that if any contributor objects, they will remove that person's contributions on request. But US law doesn't actually require that. In the US ( http://copyright.universityofcalifornia.edu/ownership/joint-... ):

"Each joint author has the right to exercise any or all of the exclusive rights inherent in the joint work. Each author may:

"• Grant third parties permission to use the work on a nonexclusive basis without the consent of other joint authors

"• Transfer his or her entire ownership interest to another person without the other joint authors' consent".

In other words, unless you have some kind of enforceable agreement between all contributors, any contributor can relicense the work, without the consent of the other contributors. I'm not sure whether the GPL qualifies as the kind of agreement that could prevent this; the FSF has spent years saying the GPL doesn't meet all the standard requirements of a contract because it doesn't need to be a contract. The FSF famously requires contributors to transfer their copyright interest to the FSF because Stallman says an attorney told him that makes it easier to enforce the GPL. Or, as Eben Moglen says ( https://www.gnu.org/licenses/why-assign.en.html ):

"If there are multiple authors of a copyrighted work, successful enforcement depends on having the cooperation of all authors.

"... [I]n order to be able to enforce the GPL most effectively, FSF requires that each author of code incorporated in FSF projects provide a copyright assignment, and, where appropriate, a disclaimer of any work-for-hire ownership claims by the programmer's employer."

Many open source licenses other than the GPL don't have any chance of qualifying as the kind of agreement that could prevent a single contributor from relicensing the project on a whim.

Also note that "contributor" doesn't necessarily mean to "contributor to the parent project." I haven't been able to find any legal reason somebody can't fork a project (following the license), make enough changes to become a joint copyright owner as far as their fork is concerned, and then relicense the fork. I guess the original contributors would also be joint copyright holders as far as the fork is concerned, and could relicense the fork as well. I'm not sure where that would end; and I'm glad that so far nobody's been creative enough to start such a battle.

So, back to LLVM: Apple is, without question, a joint copyright holder and can relicense the code as desired. De Raadt's idea is that a European could say "well, the relicensing was OK under US law, but not under European law." But I don't see how moral rights would prevent relicensing. The Berne Convention establishes moral rights as ( https://en.wikipedia.org/wiki/Moral_rights ):

"Independent of the author's economic rights, and even after the transfer of the said rights, the author shall have the right to claim authorship of the work and to object to any distortion, modification of, or other derogatory action in relation to the said work, which would be prejudicial to the author's honor or reputation."

Note, (1) that is "independent of an author's economic rights" and (2) the contributor has the ability to object to any modification, mutilation, distortion, etc., of the work; not of the terms the work is distributed under. Countries can establish their own idea of moral rights, but I'm pretty sure they will follow the Berne Convention's definition pretty closely.

So I would predict the outcome would be a court opinion that any contributor has the right to change the license, and that moral rights aren't the right tool to stop a relicensing. And if anybody can fork, become a contributor in the fork, and relicense the fork, I don't see how anyone can enforce any license restrictions.