Cyanogen are known for development and developing custom ROM is their hobby. Although, Cyanogen may now be working towards releasing its own hardware with rumored partner Oppo but that doesn't mean they'll forget about custom ROM and since Android KitKat 4.4 is here they'll have more fun developing it.
Cyanogen introduces "CyanogenMod 11" custom ROM for the Samsung Galaxy S4 representing KitKat in a whole new style. Instead of the numbering system that Google follows to represent Android build nickname they have used "CyanogenMod 11" because K is the eleventh letter of the alphabet, which represents Kikat in Cyanogen's style.
Since the ROM is in Alpha state it does have some bugs including non-working screen auto-rotation, low microphone volume and no video recording.so it’s only suitable people who are willing to help with finding and fixing bugs.
And if you are willing to to get your hands on the unofficial CyanogenMod 11 alpha ROM and experience pure Android 4.4 KitKat on your Samsung Galaxy S4 I9500. It is available with the Instructions on how to install it.. Click here to download (XDA link)