Despite having a computer for the past 3 years now, I've never participated in a game jam before. I'm worried because 

A) I don't know if I'm skilled enough to finish a game in 3 days

B) I have school starting on the last day of the jam

C) I'll only be able to put about 3 hours of work each day into the jam

If I join the gamejam, am I obligated to finish it? And is it ok if I turn in a really bad game?

Cheers,

BurgerFa- wait I don't have to sign my name

If I join the gamejam, am I obligated to finish it? - no

And is it ok if I turn in a really bad game? - yes

Just go for it and make something you think is extremely small and easy to make, I'd say. It's just for fun  :)

join the jam, you don't have to finish, just try, and if you finish it and it's trash, submit it anyway, any feedback can help improve it, it is really just for fun.