Earlier quoted context omitted.
Github is a completely optional thing though. If it were to die tomorrow, everyone still has the code locally, and code sharing is still very much possible.
You were the person who wrote "Eg, on github."
The main reason to mention github at all is that it gives me stats. There's probably a bunch more repositories out there just from people doing git clone, but I can't count them.
Also, while github helps it's not a critical part of the whole thing. If it disappeared it wouldn't be a critical problem. Everybody would still have the source, and could figure a way to reconnect again.