> That said, doesn't seem to offer a compelling alternative to Github

I have limited (but at lease some) experience in working with GitHub Enterprise, and for the longest time, their answer to backup was to turn the entire system offline while you performed the backup. I believe they have since improved in this area, but it was clear that while GitHub itself offers an extremely available service, GHE is severely lacking in this respect.

CodeCommit on the other hand promotes high availability from the start.