The Firefly Universe Online game from DarkCryo seems to still exist. I do wonder why this hasn’t disappeared yet; they’ve gone so far as to have illustrations of Mal and River there - computer generated graphics, now, not photographs - and are making heavy use of the brand name. There’s even a Facebook Page, and implications that the game is in an alpha stage. I am not a gambling man, but I reckon poker would be a better bet than this game making it to a commercial release.
Meantime, the Multiverse Foundation is still going along as well. Looking down through the FAQ, though, they seem to be headed in the direction of a generic open-source MMO. I’m not convinced of the likelihood of success there, either, to be honest - what I’m seeing more and more of in successful games is a tight integration of game and setting, and if you’re using a generic engine, that doesn’t work so well. Indeed, that much is clear even in tabletop MMOs - there are very few generic systems in wide use, and a hell of a lot more genre-specific games.
There’s no other motion out there on Firefly, but I’m keeping a close eye. With all the fuss over Kickstarter and similar crowdfunding facilities over the last few months, I think it’s only a matter of time before we see some sort of Firefly game there.