I also find this usage to probably be viewable as abuse, but clearly GitHub has chosen to continue allowing it, even as it has caused them issues like this. I think for them, it has provided some interesting insights about their infrastructure and areas they can optimize (not necessarily because they are lacking). Besides the work they put into this, I can think of at least one other noticeable change they made, which was how the repo pages displayed
huge file lists (CocoaPods used to have a
massive list of files at the root).
So yes, it's probably not great, but it has given GitHub some fun inf. challenges to build to. If it was something they felt like they couldn't handle, I'm sure they'd politely ask them to hop off their platform ;)