How to keep your programming partner motivated?

Working on a project with a programmer where we are splitting potential revenue. It has become very hard to move the programmer along and get to a shippable app. He has a full-time job which I understand but if we want our project to be successful we have to get the app to a shippable state. He refuses to set timeline goals.

Anyone have any ideas on how to motivate a programmer to get something done when you are not paying him?