Yeah, I was a GitHub user in 2008. Though it obviously had a social aspect, it wasn't considered a "social network" type of site. Its ongoing transformation into one is a result of the acquisition by Microsoft.
I have always considered it a social network, 'the social network for young programmers' as I called it, which turned free software into social networking (portfolio for first employment(s), etc.), and that's why I always refused to create an account over there as I don't want to push those things even further, and got gradually more appalled as I watched projects following the trend and moving there one after the other, making themselves more and more dependent of the tools conveniently provided by that silo, and cutting other ways to interact with them. Long before Microsoft entered the picture.