Another possible backup is any host on the internet. Seriously, dump it into a static file directory on any old web server or run a trivial git server. Send deltas with patch files. It's not even harder than github is, just uglier.
If you want to use your own servers, Atlassian (who own Bitbucket) recently released Stash, a competitor to Github Enterprise. Pricing is very good and if you have a commercial license, you also get the source code.
(I'm not affiliated Bitbucket in any way. I don't profit from them doing well, aside from them sticking around to keep providing free hosting for me.)