Nop, no restrictions (well, at least nothing I'm aware of).
I have no problam what-so-ever running anything on my bsd (fine OS, if I might add).
Say, on another note, did you have any trouble compiling aMule 2.xx?
I guess there isn't any port of this version (being RC and so), hu?
(sometimes I wonder how people manage to live without ports, I mean, in the begining, compiling was fun, but you get tiredsome after a while..."need that, depends on this, headers not right bla bla bla")