Aperture still doesn't use the native OS X tools for file browsing. It is the most un-Mac like product I've ever used.
The image framework was originally based on OS X Core Image, which was, I assume, a descendant of the NeXT imaging engine. So did Aperture start out as a NeXT photo management tool?
Unfortunately I can't find anything on the net about NeXT photo management software -- perhaps because NeXT died when the web was young, and also because "NeXT" is a useless search term (modern search engines are not case-sensitive).
Perhaps Aperture 1.0 was an acquisition, but I don't see any likely suspects on Wikipedia's Apple mergers and acquisitions list. Perhaps it was designed to be sold on Windows as well as Mac OS; but then why not emulate iTunes?
It's a puzzle. If I had to bet, I suspect it has roots in NeXT. I don't think it's de novo OS X development.