Short version of it is, gorhill actually willingly gave the project away to a contributor who later started to ask for donations. This was not appreciated (hence the very explicit "no donations" policy gorhill now has) and caused a bit of drama and gorhill started developing his own version again. This part I didn't know, but apparently he's not that bitter about it as the guy who took over the project is quite young. https://github.com/gorhill/uBlock/issues/130#issuecomment-96...
If i recall correctly, they have the same name because they were once the same project. Renaming would likely break many workflows/bookmarks that people use to tell the difference. Maybe mirroring the existing repo to another with origin in the name would be a compromise?