I never said it was "impossible if you're willing to rewrite the kernel to do it", but you imply in your posts that it's somehow possible with Xpostfacto or whatever, and the point is, no, it's not.
(MkLinux uses an older version of the same Mach microkernel as OS X and runs on a few NuBus Macs... badly. Someone with enough time to waste could undoubtedly start with the Darwin and MkLinux sources and after many, many man-hours of work spit-and-baling wire something together, and if you want to do it have at it. But unless you have a reference demonstrating otherwise so far as the OP is concerned that work has not yet been accomplished and therefore it is "not possible" to install OS X on their 1400..)