I recollect quite a similar incident with a friend of mine who had high motivations but lack of willingness to pursue the product they started. I believe you either need to talk this out clearly and define milestones on what you expect him to do. If the milestones are complete in a given period of time, nothing like it. If he still doesn't put efforts to contribute, then I would recommend that it's time to have 'the talk' with him whether he would like to pursue this further, or not.