Earlier today, HTC started rolling out the Android 4.4 KitKat update for the Google Play edition of HTC One. Along with the OTA update, the company also published the framework files and the source code for the KitKat update.
The source code and framework files would allow custom ROM developers to develop custom kernels for the 4.4 KitKat ROM for the One. It would also help the likes of CyanogenMod and other custom ROM developers in ironing out the bugs in their KitKat based ROMs.
Samsung has also released the source code for the KitKat update for the GPe edition of Galaxy S4, even though the company is yet to start rolling out the OTA update. However, with the source code released, the final OTA update should land today itself, or at the very maximum, tomorrow.