Hi Stan,
the snippet from your configure.log just shows the output from the uname program, it doesn't indicate that it ubderstands what that means.
MacOS X uses a more advanced (and slightly quirlky) mach style of dynamicly loaded libraries that is different to most of the gnu world.
If you want to have a go at porting it yourself you will need to know about the two types of dynamically loadable code in OSX - check out the fink porting tips page for a somewhat brief introduction: