I don't think it's really in Mojang's interest to actually enforce those rules. The majority of servers I've ever been on have a "Donation" system allowing you

I don't think it's really in Mojang's interest to actually enforce those rules. The majority of servers I've ever been on have a "Donation" system allowing you to buy in game perks (currency, commands such as /fly, etc). Incentives like that are what keep lots of servers up, and more people playing the game.