Ask them to sign over all rights for the company to you. Prepare to be busier then you've ever been. Launch. The worst case scenario could be that you get no users... if that happens, search out a new partner, it should be easier to find one with a prototype already built.
If the other worst case scenario happens and you get a lot of users, good problem to have! Find some more help at that time.
You are on the cusp of succeeding or failing. Nothing has been determined yet, and don't let your partners decision to do nothing stop you. Oh, and it sounds like they haven't done anything yet.
Next time make sure your partners are putting in as much effort as you are along the way so that you aren't the only one with flesh in the game and they along for the free-ride.
If the other worst case scenario happens and you get a lot of users, good problem to have! Find some more help at that time.
You are on the cusp of succeeding or failing. Nothing has been determined yet, and don't let your partners decision to do nothing stop you. Oh, and it sounds like they haven't done anything yet.
Next time make sure your partners are putting in as much effort as you are along the way so that you aren't the only one with flesh in the game and they along for the free-ride.