Umm, LimeWire is also Open Source. How else could FreeWire be based on it? (it's not all that different from LimeWire actually, and they have a suspect installer) There is more than one project based on the open source LimeWire code, mine among them (AquaLime)

Oh, and clustering sucks. But why get worked up over it? If you don't use BearShare, it doesn't really affect you. You can't find the files on BearShare users HDs, but they can't find the ones on yours, so it's not like they'll leech or anything. They'll just find themselves isolated. Oh well.