> their own window manager and app framework on it only
Window manager in this case including Quartz/Core Graphics (replacing Display Postscript) as well as complete UI facelift/transplant that turned the NeXTSTEP file browser into the Mac OS X Finder (even if it imperfectly copied the spatial orientation of the classic Finder.)
App framework being not only a Mac flavor of AppKit/Foundation/NS* (Cocoa) but also a virtual legacy Mac OS layer (Classic) as well as a hybrid API (Carbon) that worked on Mac OS 9 and OS X, providing a fairly complete Mac app transition strategy (classic -> carbon -> cocoa).
Cocoa also worked with the (later abandoned) Java bridge as well as Objective-C++ and OSA/AppleScript/etc.
Window manager in this case including Quartz/Core Graphics (replacing Display Postscript) as well as complete UI facelift/transplant that turned the NeXTSTEP file browser into the Mac OS X Finder (even if it imperfectly copied the spatial orientation of the classic Finder.)
App framework being not only a Mac flavor of AppKit/Foundation/NS* (Cocoa) but also a virtual legacy Mac OS layer (Classic) as well as a hybrid API (Carbon) that worked on Mac OS 9 and OS X, providing a fairly complete Mac app transition strategy (classic -> carbon -> cocoa).
Cocoa also worked with the (later abandoned) Java bridge as well as Objective-C++ and OSA/AppleScript/etc.