Based on Ancalagon's suggestion I've whipped up a quick tree of some of the spinoff boards from TrekBBS over the years. I know there's a lot more I'm not remembering or simply don't know about. I'm also not sure where Lonaf had fit into the tree either.
There was also StarscapeBBS and Lisa's spinoff board dedicated to Captain Janeway I don't remember what it was called. And then Borgs tried to spinoff a board from Wordforge dedicated to torrents and illegally downloading stuff. There's also Volpone's spinoff board which is magically invisible and Scorponok's board which no one was invited to.
I'll talk to Eggs to verify Lonaf, but I believe Lonaf's an EFCL spinoff, with HavenBBS and at least two other boards as direct child boards. Also: EFCL -> REFCL -> Last BBS
The adult board that BlackDog started after TrekBBS was all "stop sending each other nudes through PMs" didn't make the list? Although, that was a "secret" board so maybe it shouldn't have made the list? Naughty Nerds was fun. I tricked everyone into looking at my penis. Only it wasn't a trick and everyone looked at my cock of their own free will.
I was on the TK, Shattered Corpse, Exile, LoNAF, and Haven. Originally I was at Slipstream. Then along with twelve others, we got perma banned and washed up at TK
I can't believe someone else remembers Orb Hall and Dark Kingdom! Dark Kingdom was the board I made when TK was slowing down. I went back to school for three or four months and I left RobL in charge as an admin. When I came back he was still running the board and even made some new upstart named MissManners an admin! I wonder what ever happened to those two.
Apostle83 (now Ron Paul here) had a spin-off board. Well, it was more a place he and Enterpriser could mutually masturbate. Can't remember the name though.
I vaguely remember another board that I agreed to mod at briefly, but I can't remember the name, who started it, or what kerfluffle led to its creation. It was pretty low-traffic and short-lived.
Some of you posted once or twice on a board I started, that was hosted by Borgs for a short time. Does that count?