GitHub was hosted on Engine Yard[0] in the early days, and as part of that deal had an Engine Yard banner in the footer. We then moved to Rackspace[1] for a few years until the first funding round in 2012 when we built out our own datacenter in earnest.

[0]: https://github.blog/2008-05-07-rolling-with-engine-yard/ [1]: https://github.blog/2009-09-15-github-is-moving-to-rackspace...