Mcmmo is a nice plugin however its more used in pvp servers and it would ruin the vanilla feel of EMC.
Sadly, Justin doesnt code them all. I say sadly because when there is a MC update Justin it's up ahead and the external plugins delay the whole EMC platform
This plugin completely destroys Vanilla Minecraft.. Its fun of its on volition.. but would ruin the vanilla minecraft feel.
He does a ton of coding for EMC though. Also if you want something different: You can download and install with an exe and not even alter your minecraft. http://www.technicpack.net/launcher/
Considering modifications to the original plugins as a "code for EMC" then it's true, but plugins as Multiverse, residence and dynmaps aren't 100% Justin's. That's what i mean
According to: http://mcmmo.wikia.com/wiki/McMMO_Wiki McMMO's main function is to incorporate an RPG-like skill system that players will have access to right from the beginning. Depending on how much a certain tool is used or a certain action is performed, players will gain experience that will eventually add bonuses such as double drops, rare drops, or ability enhancement. Basically sounds the same as Hack/Mine in the Technic Launcher.
Either way if you want a plug-in implemented you have to convince Justin/ICC/Twitch1. If it involves altering the Empire Servers it's automatically gonna be denied because EMC is a legit, mostly vanilla Minecraft server.