not that actually, its the EULA thing... I looked over it and it seems quite stupid. Even notch's address towards the people hating the EULA was bad at best, one of his reasons being parents are mad because they lost a lot of money because their kids bought stuff without their permission... REALLY... you decided to do that EULA because parents don't keep track of their kids...
Any tools you write for the Game from scratch belong to you. . Modifications to the Game ("Mods") (including pre-run Mods and in-memory Mods) and plugins for the Game also belong to you and you can do whatever you want with them, as long as you don‘t sell them for money / try to make money from them.
This is a direct quote from the EULA. So, this means that servers like mineplex cannot sell the classes and ranks because thats all plugins, they can just ask for donations, which has been proven to fail by a mindcracker. It's just frustrating to me...