Four months have passed since the OP started this topic and by now the
latest DF release has full EFI support. I was able to halfway* netboot the install image on my macbook, and can confirm that the EFI boot code works. At least on my machine.
(*) Halfway, because during boot it dropped me into the kernel debugger. But this has either todo with my netboot setup or perhaps some unsupported part of my macbook. I didn't investigate further, but it wasn't EFI-related.