This looks great for more experienced programmers. If you're working with younger kids, using Minecraft as a way to introduce programming, here are some good options:

* Minecraft Pi - code and run Minecraft mods in Python (https://www.raspberrypi.org/learning/getting-started-with-mi...). If not running on a Raspberry Pi, you can use Raspberry Juice (http://dev.bukkit.org/bukkit-plugins/raspberryjuice/) which implements most of the Minecraft Pi API.

* Scriptcraft (http://scriptcraftjs.org/) - create mods using Javascript.

* LearnToMod (http://www.learntomod.com/) - commercial service that allows modding using a visual language (I think they use Blockly which is similar to Scratch).