[semi-extrinsic]

The way I understand this is not that Github Pages can't be used for commercial purposes, but that it's not OK for something like ecommerce with many users every minute which generates a lot of load?

So a small company could host a static landing page with generic info and "contact us" etc., and that would be fine, I think?

It also mentions that breaking the rules will result in getting a "polite email suggesting ways to reduce load on Github".