Earlier quoted context omitted.
Being the _the_ place for open source is what let them dominate the enterprise. Now that they dominate the enterprise, it'd make financial sense to put hard limits on the free tier. It's cynical but it would be foolish to lose that cash machine. It'd open them up for a competitor to slowly build up good will in open source then take them on in enterprise, but right now they are risking losing it all.
Big enterprises are on a different github deployment, so I doubt they are affected by this
(maybe F500 people have their colocated box, but I have the impression that those are the "first class" seats (very expensive but _very few_) whereas enterprise cloud is the "business class" (loooooots of seats making a lot of money)