FusionForge is not a huge project (Ohloh lists 21 contributors currently), and we don't have a very formal organization.
Our project is merely a do-ocracy (i.e. those who do something are deciding by the action of doing it). If you recall the initial FusionForge announcement, one of the goals of the project was to have an explicit and transparent governance model. We have so far fallen short of that, and although we believe we are more transparent than we used to be, there's no formal decision-making process. So far (after a year of existence), we haven't been facing a decision point where consensus wasn't reached. The motto of the IETF ("We reject kings, presidents and voting; we believe in rough consensus and running code") could therefore be said to apply to FusionForge too.
For questions that go further than simple technical details, the decision system is currently to discuss them on the #FusionForge IRC channel (on the Freenode PDPC IRC network) during the weekly meetings which are held every Friday at 13:30 (1:30 PM), Western European time (TZ=Europe/Paris), which is 11:30 UTC during the summer and 12:30 UTC during the winter.
The meetings are open and can be accessed with a browser with the following link: Web access to #FusionForge IRC