Minecraft users can create their own servers. minecraft tekkit servers has been a double-edged sword. It is a low-res, blocky sword, but it's sharp on both ends. Players can do just about anything they would like on these servers which is great, however they can also get into trouble for violating the game's EULA and this can land Mojang's developer in hot water.
"Some privately run Minecraft servers do charge for in-game items like extra xp, or access to certain game modes. In a blog post, Markus "Notch", Minecraft creator, noted that some of these servers may charge quite some money. "I do not know how many emails I have received from parents asking for their hundred dollars back that their child spent on an item package on a server that we don’t control."
Mojang has established new rules for monetization to make sure that there are no such accusations in the future. Mojang has detailed the rules on its website, however it's basically a matter of removing restrictions on creating in-game items or other monetized products. Just make sure to communicate with your customers that you're not Mojang and don't offer items that impact gameplay, and don't charge real-world money for in-game money.
Oh, and another thing: Persson's request "Herobrine Please stop asking." [Image: Mojang]