Hi, I'm actually the lead dev (Paul works with me, but is a recent addition to the project). Glad to see the interest on here.
Our funding is down on that page under 2011, it comes from the Rita Allen foundation. We do get paid a fair rate (I'd say, granted it isn't what we could be making in some places but it isn't that far off, plus I get to write open source code all day and do something I care about.)
It looks like it's an in-house project at the Sunlight Foundation, by paid staff. The primary dev (going by GitHub checkins) seems to be Paul Tagliamonte, who is a Sunlight Foundation employee: http://sunlightfoundation.com/people/ptagliamonte/
I ask because I am interested in some non-profit work, and I am curious if developers on non-profit projects find ways to get paid a fair rate for their development work.