For sure as of today GitHub is a web app, but it's questionable whether it should forces you to use it as one. In essence, GitHub is just a remote server for a .git folder. This does not need any JS.

I see that GitHub now tries to become at the same time a social media for hacker-friendly people and some sort of super-CI server with automation. For sure these are good features. However I also see why people are sad that the old (and defining) functionalities stopped working without JS.(look at commit, browse the sources, read and submit issues / PR and code review). It saddens me a bit to often see working websites getting more and more complex, adding more and more features, probably to remain "fancy" and competitive.