The commentary here, reminds me that no one has jumped up and down and said, but its not really Mac OS!!!! It's really just FreeBSD with a Mac layer!
Of course not...it is Mac OS.
I know, I come at things sideways, but I'm thinking about the whole discussion once upon a time about the next version of Amiga and using QNX or Linux core, and especially Linux, to jump start Amiga OS development.
Amiga Inc. would have still had their work cut out for them, developing the higher level Workbench that ran on top of the Linux core, and I think no one, would have claimed it was really Linux...or at least, such an idea wouldn't have gotten any traction, any more than we think of Mac OS X is FreeBSD...even though in fact the core is based on FreeBSD 5.0.
It's all history now...but basing the new Amiga on Linux, would have gotten us a modern system, that would have been a true Amiga....get a modern looking workbench, use some of the Amiga concepts, Arexx....
In point of fact, its still the way to go with Amiga...if they want to revive things at this late date.
Anyway...I agree with you whole heartedly, Mac OS X 10.5, at a certain level, is what Amiga OS could have been.
Fast, fun, powerful....every machine comes with standard development tools in Xcode. Heck, even before Amiga...in the Commodore 64 and Atari 800 days, what I liked is they always came with Basic, and anyone could tinker with it.
Anyone who has Leopard, can do a program tonight....if they want to start tinkering...and that is really cool. Although I have to admit, even in the Windows arena, Microsoft giving away express editions of their compilers...even if not installed by default, is still a cool move.