It’s relatively easy to self host your own git repositories.
It’s just that Github adds a lot of extra value added features that help streamline things for larger projects, and this is why many people use it. For most people, the value they get far outweighs the inconvenience when it goes down for 10 minutes here or there.
Google (used to) scrapes the specific details authorized by robots.txt and uses it to make your content visible.
OpenAI scrapes everything it can technically see, ignoring robots.txt and feeds i to a black box and regurgitates it claiming it’s something new, that it deserves to be paid for.
Quite different actually.