They advertise no jobs at all outside of San Francisco and Houston. They base everything on GitHub, screwing over those of us who have been using Sourceforge, Google Code, Bitbucket, or some other open-source hosting service since forever. The first problem they can fix; the second is the fault of basing a business model on the institutionalization of the fad for GitHub.
Those are both non-issues. They're a startup. Their product is a two-sided marketplace, naturally geographically limited. Any other open source hosting service would do just fine. It may happen that github is the most insular and the one most likely to have a critical mass of programmers in certain skill sets (it seems to massively dominate for Rails folks).