Please note that I do not want to argue about the moral aspect of this question. I know that there are probably many different concerns.
I have been researching for a special license that could be used in a following scenario, but with no success:
Let's assume I have a software and want to release its source code, so that others can use it too. Since I don't want others to make changes and keep them closed I could the GPL. But here's the thing: Even if I profit from changes that other people do. I can relicense only my code because I'm not holding the copyrigth any code that not made by me. But I would like to.
I want to know if there is a ready-to-use license that will grant me (the initial author) the rigth to relicense any changes or code that was added by others. Or in even shorter terms: A GPL that does not count for me.
If you are interessted why I need this: I don't know if I will ever use my software for a commercial product. Probably not, but if I just use the GPL, I migth end up in a situation where I can't remove any other code since there are to many committers.