Comment by esperent

> The license does not bind the original copyright owner, who can do anything with the code

For any small to medium sized projects with zero external contributors, it's highly unlikely that anyone would pursue legal action so the person who owns the project does de facto have this right whether or not it's legal according to the license.

> Things get more complicated if there are external contributors

I don't think this is complicated - unless there's a contributor agreement that people have signed that says otherwise, people have copyright on the code they have contributed so the original creator doesn't have a right to relicense their code.

However, again it comes down to whether anyone would bring a legal fight and the answer is almost certainly no. Forking the code is much more likely at that point.