Later. Keep the project requirements small until it's working well. Get it to serve one desired purpose very well. Only then look at extending its use.

This is true for any coding project, but an order-of-magnitude more true for a volunteer project. If you want to get a programmer to actually volunteer for a project, convince them that the project will see great rewards while it's still small. In fact, you basically want to maximize intuitive value, while minimizing expected work. It feels so much better when your actual, original goal is achieved with a small amount of work than it feels when your tiny, first step is only the start of achieving your goal.