As same as Android OS, Jolla Sailfish OS is the open source mobile operating system, this OS can be used freely for public. And now Jolla has been launch officially the stable version of Sailfish OS for LG Nexus 4 smartphone.
The LG Nexus 4 user can port the Sailfish OS to their phone is very easy, the trick is same as porting the custom ROM to the Android phone. If you want to porting the Sailfish OS to Nexus 4, the phone must be rooted and running CyanogenMod 10.1.1.
And then, you can download the Sailfish OS at http://releases.sailfishos.org/sfa-ea/sailfishos-mako-release-188.8.131.52-EA1.zip this file is contain 354Mb of file size.
This is the early version of Sailfish OS, so it may has some bugs and lacks of features, so there is no calling featuresm no Bluettoth support, no alarm function, while the phone can’t take the video due the camera is not work and the sensor is off too.
But Jolla is trying to keep update this version to work with Nexus 4 smartphone in the future.
You just might want to make a nandroid backup of your device using CWM, TWRP, or a similar tool first so you can restore it to its previous state when you’re done poking around…. just don’t expect it to replace Android as your primary operating system just yet.