The last time I checked, GitHub has 0 ads on it. And they're clearly not making any money off of their users, because features like paid accounts don't exist. It's impossible to monetize a product without slapping tons of intrusive advertisements all over the place.
https://github.com/settings/billing says otherwise, mate. I assume the sarcasm was to the fact that you can't make money without ads, as opposed to being sarcastic about having no paid accounts.
/s