If you want to go really minimal you can do raw git+ssh and hooks (pre/post commit, etc).

i would imagine that's what everyone is doing instead of sitting on their hands. Setup a different remote and have your team push/pull to/from it until Github comes back up. I mean you could probably use ngrok and setup a remote on your laptop in a pinch. You shouldn't be totally blocked except for things like automated deployments or builds tied specifically to github.com

Distributed source control is distributable.