Cuberite is a Free and Open Source (FOSS) Minecraft-compatible game server. Cuberite is designed with performance, configurability, and extensibility in mind, and also aims to accurately recreate most Minecraft features. The server is written in C++, and there is an extensive plugin system that allows for the user to write their own plugins with Lua.
The current version works with Minecraft 1.8 - 1.10, but we recommend playing on Minecraft 1.8, as Cuberite lacks a few Minecraft 1.9 and 1.10 features.
You can find the source of Cuberite on GitHub: https://github.com/cuberite/cuberite
And you can also find the source of this app on GitHub: https://github.com/cuberite/android