The version you'll have seen is the original version that I "leaked" to someone else who wanted to run a similar site. I said they could make the code public, but I didn't want to maintain or stand by it. It underwent an entire rewrite about ten years ago which is the version that's live now and the auth flow has remained the same within that timeframe, at least, but https://github.com/omniauth/omniauth-github does the heavy lifting and has been updated as a dependency in that time.