I'm sure a could read a bunch to find out your answer, but it wasn't quickly enough obvious to me (as a programmer) how you ensure the scope of work is actually equal to $3500 of my time.
As a university student, this is really pretty great. I will have the opportunity to work on reasonably sized projects, earn some extra cash, and probably build a pretty sweet portfolio. I even think it would be cool to form student orgs around this - have upperclassmen train underclassmen in the art of full stack web-dev, and then have let two underclassmen jump into one of these projects with the guidance of an experienced dev. Finally, split the profits. If any of the founders are reading this, would you be open to something like this?