A new version of LZVN is available for download – the source code that is. You can compile LZVN by running make in the project directory. Do note that you need the Xcode command line utilities.
Unpacking of a prelinkedkernel can be done with
./lzvn -d /System/Library/Prelinkedkernels/prelinkedkernel prelinkedkernel_unpacked
Repacking of a prelinkedkernel can be down with
./lzvn prelinkedkernel_unpacked prelinkedkernel_repacked
This will inject a new (fixed up) mach header, which is stripped off when you unpack the prelinkedkernel. The end result should be the same as the factory kernel. You can verify this with
cmp -l /System/Library/Prelinkedkernels/prelinkedkernel prelinkedkernel_repacked
Yes of course! You can still unpack/repack any file with LZVN.
Update You can now also extract the kernel from a prelinkedkernel. For this you use:
./lzvn -d <path/prelinkedkernel> kernel
Have fun with it!