In my work, clients mostly need a site built to perform a specific function, and if Habari fits that task, I use it. There isn't an explicit demand for Habari developers, but there is a high demand for sites that Habari is suited to produce, which overlaps a bit with WordPress' capabilities.

As others mentioned, the main habari/habari repo commit count is low because the main development doesn't happen there, but in a submodule'd repo, habari/system. The purpose of this is to allow you to easily fork the main repo to add your own plugins and themes to it, while the submodule continues to pull from the system repo. It's very beneficial from a maintenance standpoint.

I'm not sure how to explain the community. My involvement has been nothing but beneficial for me, and it has been a similar experience for the people I know the community has touched. Development has been reasonably continuous, as you can see here: http://www.ohloh.net/p/habari

The work happens at https://github.com/habari/system, which is very active.

I can't answer for @ringmaster, but for me it's client work, though it's a sideline to my main job at the moment.

Code is maintained in https://github.com/habari/system

+1 for Habari, especially for keeping it relatively sane compared to WP.