At first I thought that it's his project, if he wants to un-open-source it, I guess he can. But then I considered the contributions that others have made to the project. Can he un-open-source those?
No, but many companies (and the FSF) demand that contributors assign copyright to any open source contributions they make. Sometimes they make excuses about how owning copyright in all the code makes it easier for them to go after license infringers, but that's just an excuse; what they really want is the ability to relicense contributors' work in the future.
No, but many companies (and the FSF) demand that contributors assign copyright to any open source contributions they make. Sometimes they make excuses about how owning copyright in all the code makes it easier for them to go after license infringers, but that's just an excuse; what they really want is the ability to relicense contributors' work in the future.