"Millions of people and businesses depend on GitHub" Well, we shouldn't depend on it so much. I shudder at the thought what an outage of GitHub would mean for our company. This time, we were lucky as it was during the night in Europe. Unfortunately, I don't have the power to test this scenario in our company.
It shouldn't really have much effect. One of git's major selling points is that it's a DVCS, meaning that everyone has a local copy of the repository. Perhaps some collaboration features will be down for a couple of hours (which I think is a downside to GitHub's decision not to put issues/PR history inside of git), but everyone should still be able to do work, commit to the repo, review history, and so forth. If you…
You're right in that you're (probably) not totally deadlocked. But I can't start to estimate the lost $$ in productivity that comes with a global GH outage because of all that.