Earlier quoted context omitted.
It's a good thing git is a distributed system. In such cases, people can just switch to a different remote and push their branches there (with some care, of course).
But most people never use the distributed part of git, other than having the repo on their local computer.
The real problem that we should be talking about is - Pull request based workflow many companies (including mine) have adopted. Which doesn't work when github goes offline.
I hear from lot of teams, they have switched to using github issues for project managment entirely, so as pull request and tickets can be "seamlessly" linked. That goes out of window as well.