HQ also have it's own forum. Glorantha does not, and is a setting several will probably use for BRP, so a own "rule-less" forum for Glorantha
could be justified if the activity would sustain it (I'm just not sure if it would, as Glorantha have been around for a LONG time, and no Glorantha forums are up and running).
The great
Call of Cthulhu forum have several setting specific forums, and if the activity in the future rises to support more than one forum, I'll add it then. But for now, for a game which rules aren't out yet even, I think one forum will do.
SGL.