Realistically, disk filesystems have to be linked into the kernel (FUSE isn't going to cut it: too slow, and can't be used on boot), and Apple isn't going to li

Realistically, disk filesystems have to be linked into the kernel (FUSE isn't going to cut it: too slow, and can't be used on boot), and Apple isn't going to link GPL code into their kernel. All the stuff you listed is userspace.