C'mon guys, I slept all day and no one made a thread?
It's real, confirmed by GStaff on the official Bethesda boards. Obsidian is developing, which means some old Fallout vets will be used. Release is Holiday 2010 from the look of things. It is a side story, not Fallout 4, and is labled "action RPG"... which could mean the same thing as Fallout 3, or more action-oriented.
They also mention this will not effect Todd Howard and Bethesda's current project, which is most lilkely TES5.