Exactly. This is what I needed to hear, as a 3rd-party fan of Github's product, who is concerned by Julie's allegations. I don't know who is in the wrong, and I want to know the truth, and I hope Github can solve these problems. This statement doesn't downplay; this statement doesn't evade, and that's what this situation warrants: a serious and sincere investigation.
That was also my first reaction. I don't know enough about crisis-management-style PR to second-guess their response. I often have the suspicion that founders are not taking the best course of action, but this response seems to avoid the obvious pitfalls.
This was also my first reaction as well - the real question is how they followup this response, but this is the only correct move at this juncture.
I think the follow up will be more critical, especially the public explanation. That will have the potential to either strengthen GH's credibility or destroy it.
Why should they give a public explanation for something that should've stayed internal in the first place? This should've stayed between the OP, GitHub and GH's HR team.
One thing he could have done better is to praise her contributions as a developer specifically or not call anything out specifically. One of her main complaints is having her pull requests reverted and Chris Wanstrath's post does nothing to support her in this matter.