Actually only grouper was a sdk port. The n4 is completely based off the n5 and n7 preview images and 95% functional with only a few more bugs to work out. M7 is based off the n4 port.
N10 can be ported too but it will be tougher. I'll start working on it once I finish up nexus 7 LTE and we get the rest working on the m7. There is also port work going on for the gnex but needs some kernel work to get it the rest of the way.
The GPL released code was practically worthless other than figuring out what the changes were for L and what needed to be done since the ramdisk files were updated for everything except for exactly what is needed in L.
I'm gonna need the second set of preview binaries that google released though, the ones date 6/27. Any newer than that and they aren't compatible with the preview images, unfortunately all I can track down is the newest ones which have GPU drivers that are too new
XDA Developers was founded by developers, for developers. It is now a valuable resource for people who want to make the most of their mobile devices, from customizing the look and feel to adding new functionality. Are you a developer?