We're going to be meeting with the lawyers in a few weeks to hopefully get official blessing for pushing any NOSA-licensed project (agency-wide) to github. A couple of my group's projects have open-source releases, but don't really practice open-source development (non-committers can't see the repo). I'm trying to fix that :)
I can keep HN posted if people care, or want to use us as a convincing tool- "hey, the federal government is adopting something faster than you are... something's wrong". Obviously, no promises that it will happen exactly as I say, because... lawyers. We just have to get past their trained skeptical conservatism.
It's worth noting, though, that NASA is not even close to a homogeneous entity. My group is one group in one division at one NASA center (and a smaller center, at that). Many groups are run autonomously by their group leads, and culture is mostly maintained at the group level. Open-source is already here, it's just not distributed equally :)