[secure]

AFAIK, they never used a cloud provider.

[ryanfitz]

Github was hosted at rackspace, here is there blogpost about it https://github.com/blog/493-github-is-moving-to-rackspace

From their blog posted last month:

As we started transitioning hosts and services to our own data center, we quickly realized we'd also need an efficient process for installing and configuring operating systems on this new hardware.