As well as the official scenarios, there are also a number of other RPGs on the message board which do not contribute towards the website's ongoing story, and have no effect on the official scenarios. Some are run by command, but most are run by other members of the site.
Unless specified by the moderator, all scenarios follow the same format as official scenarios. They usually also follow the same basic rules, although they are not usually enforced strictly.
Viper's Bar is an ongoing scenario where everybody knows your name. Viper's Bar is a cantina on Farpoint owned by General Moore, where members can go to kick back and relax in character. There are occasional organised events, but you are mostly free to do whatever you want in the bar.
Welcome to Farpoint
Farpoint is another ongoing RPG set around the base. There is usually a storyline in play that you can join, but you can ask in the discussion thread if you're not sure.
Starting an RPG
Anyone can start an RPG. All you need to do is send a message to Nick Fel with your suggestion. If it's approved, you'll get a forum to start it in. Once it's started, you're in charge of it, and you set the rules. You can post up a rules thread if you want and you'll be given mod privs if necessary. You may not delete it once you've started it, and may not lock it without permission unless the story has finished.
If you let your RPG die out it maybe be locked down so it's not cluttering up the front page. You'll be warned in advance so you can try and get it going again.