This is getting granular, but any GitHub user - whether free or paid - is bound by the Terms of Service. Yes, that makes them a customer, and they accordingly have to adhere to the conditions of using the product.
> If your bandwidth usage significantly exceeds the average bandwidth usage (as determined solely by GitHub) of other GitHub customers, we reserve the right to immediately disable your account or throttle your file hosting until you can reduce your bandwidth consumption.
The one that CP's usage most likely confronts is G.12 - found here: (https://help.github.com/articles/github-terms-of-service/)
> If your bandwidth usage significantly exceeds the average bandwidth usage (as determined solely by GitHub) of other GitHub customers, we reserve the right to immediately disable your account or throttle your file hosting until you can reduce your bandwidth consumption.