Unfortunately I can't give you links here, because both those links as I found them were on the most notorious BitTorrent tracker website in the world (and those are the exact links you'll get from the development groups' forums, too) :p
You can search for "redviper" or "openfalcon" (one word).
And I think both are later FreeFalcons. RedViper is supposedly just a re-named v4 of FreeFalcon...
But yes, there were a lot of messes with F4, both legally and in terms of fierce arguments between modders and groups in the community. Being a lurker in the community, I fortunately missed all of those - but if you think the modder squabbles in SHIII/IV communities were bad, you should feel fortunate you haven't seen the ones over F4
