I'll echo the others saying to find yourself a new director. If he's not into it, it won't get the attention it needs if it get's finished at all. That is, find a new one after talking. Politely let him know where you're at, what you're expecting and ask him if he can get it done. There's a real chance it may not have been communicated clearly. If not, no hard feelings. Let him know he's getting credit for the writing or whatever he's helped with so far and that you'll be hiring someone else for the project.
Don't burn a bridge. You obviously like the guy, even if he doesn't do this project he may be super committed to the next. I think it's true at any level, but especially the low/no budget level: you need people on the team who feel a sense of ownership of the project. When you own something, you do whatever it takes to make it happen. That's one of the main factors we consider when we ask people to be a part of our projects. We have have people at every level of the production "hierarchy" including PA's, AD's and camera ops who use the word "our movie" instead of "your movie" or "the movie" and the commitment and level of attention to detail you get out of them is amazing. Wouldn't trade it for anything.