This was addressed in the forums a few years back - Team/Collaboration Entries, circa 2008.
Short answer is: nope. The competition is for individuals only.
Here's the money quotes:
If you want to use a consultant or whatever, fine. If you want to playtest your stuff, fine. If you want to ask your friends what they think of the submission before you submit it, whatever.
But one entry per person. We are looking for the RPG Superstar, not the RPG Superstar(s).
I certainly can't give an official answer, but if you think it through, team/collaboration entries would be difficult to process.
What happens if a team makes it into the top-32 for Round 1...and then they have a falling out in later rounds...and no longer constitute a team? Is Paizo still going to entrust the remaining member of the "team" with writing the final product? Would they be kicking themselves for allowing that "team" to advance when they could have accepted one of the other entries from a single person, as the rules state?
Personally, I know they allowed team entries for W3: Flight of the Red Raven, but I just think it's much more complicated to open it to teams for this particular contest. Besides, it's patterned after American Idol, right? And duo acts never make it into future rounds. Everyone gets evaluated on individual talent. Hence, it's RPG Superstar, not Superstars...