There are plenty of customizable, user-created ROMs out there. A lot of them. But there are only a few which manage to garner the attention of mainstream developers within the Android modding community, and manage to stick around over the years. Xiaomi, the company behind the ROM itself, has decided to go the open source route, providing the details of the ROM to all those who would like to have it.
They will be releasing the source code for the popular ROM via GitHub. It won’t just be the ROM, but it will also be individual applications as well. They are currently rolling the code out now, so if you go into the source link below don’t be saddened to not see the whole shebang in there. Xiaomi plans on rolling out more of the source code in due time.