I don’t have much, except that it seems that the versions used by Safari and iTunes are different and port different amounts of the OS.

The Safari version was considerably more complete and included the entire text rendering system as well as several era-appropriate Aqua UI widgets. It feels very much like a Mac app.

The iTunes version seems much more trimmed down, using Windows text rendering and win32 widgets in place of Cocoa/Aqua in most places. Accordingly, it feels more Windows-like.

It might be interesting to try to build a toy app against the Safari version just for kicks.