Community App - Custom vs 3rd Party

Thanks to encouragement from Mark Frazier at Open World, I'm more seriously exploring existing platforms and content management systems as digital hubs for local communities. I had been thinking along the lines of a fully custom app that I could open-source, but the development and documentation overhead would be high on a project like that. Right now I'm looking at Ning and Wordpress as alternatives.

Wordpress has the advantage of a standalone installation and very strong developer documentation. A standalone package is attractive because it does not rely on third party hosting, and could operate on a local mesh network without internet connection. Ning, on the other hand, is a hosted solution and the documentation is less comprehensive. However, setup is a cinch.

My inclination right now is to prototype a solution in Ning, then create a standalone Wordpress package that can be installed on any server. I will probably end up creating custom plugins, especially for wordpress.