It will, in fact, be open-sourced.

Development is not yet a community project mainly because I haven't had any takers. That, and the project currently has no differentiating functionality to distinguish it from the hundreds of other projects like it. Once I feel it would not be a waste of the community's time to work on it, I'll set up open-registration on a Trac-hosted project.

I believe that adding solid webmail functionality to the system will give it that extra oomph it needs to solve the problems I would like it to solve, and hopefully the problems others would like it to solve as well.