The 4.4-r3 release is based on the Android 4.4.4_r2.0.1 (KTU84Q) release. We have fixed and added x86 specified code to let the system runs smoothly on x86 platforms, especially for tablets and netbooks. There are a lot of improvements since the 4.4-r2 release including
This release contains two files. One is the traditional ISO file that can be booted on devices with legacy BIOS. The other is the EFI image that can be used on more modern devices with UEFI firmware. You can choose one of them depends on your devices. In doubt, try the ISO file first.
Both files can be dumped into a usb drive to get a bootable usb stick, like
dd if=android-x86-4.4-r3.img of=/dev/sdX
where /dev/sdX is the device name of your usb drive.
repo init -u git://gitscm.sf.net/gitroot/android-x86/manifest -b android-x86-4.4-r3
Read this page for how to compile source code.