If it could use Heroku as backends for repos, now that would probably break HK's freemium model.
The other point is that bitbucket has unlimited private repos for free and github has unlimited public ones for free. In a business setting, I can't see the time and cost of maintaining code services except as a backup, or if you are Goldman Sachs imprisoning your ex-employees or a defense contractor working on missiles. (Setting up giolite + active directory + Crowd + JIRA + FishEye was a chore I'd rather not repeat.)
It looks a little nicer than gitlab, but has anyone had recent experience with gitlab, redmine or github enterprise?
Ultimately though, github could threaten C&D against the authors if it were to take off because it's such a design ripoff. Although it has almost no commercial viability it's neat for its own sake.