Sony has posted source code and binaries for the Xperia Z3, Xperia Z3 Compact, Xperia Z2, Xperia Z1 and Xperia Z1 Compact. The company is yet to release the Android Lollipop Update for these devices, however it has already confirmed that it will release it soon.
Last week, Sony announced Android 5.0 Lollipop beta test on Xperia Z1, Z2 and Z3. Google pushed Lollipop source code to AOSP last week. Developers can use the kernel source to build a version of stock Android for these devices, or use it as the basis for a custom ROM. The source code and binaries released today can be used as a base for developing your own version of Android for devices from the Xperia Z3, Xperia Z2 and Xperia Z1 series, which have an unlocked boot loader.
Sony said that there a couple of limitations like the camera is not working and the modem is not enabled, which means you cannot take photos or make phone calls. You can get more info about it at Sony Developer World.