Git, the protocol, is not the same as GitHub, the service. Git, the protocol, is absolutely distributed. And just to repeat my point - GitHub is only a single possible node in the graph

I'm not sure if GitHub fits the definition of distributed (unless you're talking about their load balancing setup, in which case - is that relevant?), but git is designed to be a decentralized store of information (specifically code, but not stricty) and optionally distributed.