Head on over to: https://github.com/MiCode for the run down of apps which have already been made open source. Other applications and code is likely to be published in the very near future.
They are currently in the process of getting everything loaded up to GitHub, which is the same location CyanogenMOD is stored. Not everything is loaded as of yet, but we fully expect to see things added in over the next few days. I hope our devs out there take a good long look the code and bring us even better MIUI based ROM’s.
Head to MIUI GitHub and get started guys.
Via Miuiandroid