Although I'm thoroughly impressed and applaud people for doing this in their spare time, I sort of wish they wouldn't help Apple in their developer-hostile actions.
If Apple don't want to release documentation on their chips, then leave them to rot in their walled garden.
I mean, I guess there are various degrees of hostility. When Apple ported their iOS bootloader to the new Macs, they purposefully added the ability to boot third-party operating systems.
They just didn't tell anyone how to actually build a third-party operating system.
Exactly the middle ground, but it's a shame so much has to be reverse-engineered due to lack of documentation. It's quite a contrast from the Apple II, which came complete with schematics and a ROM listing. Obviously, today's computers are nowhere near as simple, but I hate seeing more and more about our systems becoming jealously guarded secrets.
Nonetheless, a half-step like this is vastly better than the locked bootloaders, jailbreaking, and outright hostility of the smartphone/tablet/console world.
If Apple don't want to release documentation on their chips, then leave them to rot in their walled garden.