The NFL leaque headquarters organization is a non-profit.

The actual teams, on the other hand, are all profit-seeking entities and pay taxes accordingly.

I feel what you're saying on this since the pro leagues being nonprofits seems silly on the surface but you could say that about any trade organization really. The US has a real problem with what's allowed to define itself as non-profit (scam religions like crack churches and Scientology, fake athlete charities, etc) but I don't think Mozilla falls in that camp.