Do you know that according to copy rights, open source projects are mess. Nobody tried it in the court, but if some developer contributing to project went to court saying "This part of code is mine, I don't want it to be modified by other people", then the project could be in trouble. Nobody tried that (yet).
That's why some OS projects require signing Developer Certificates of Origin etc.
That's why some OS projects require signing Developer Certificates of Origin etc.