HISTORY
-Up to Emacs 22, the OS X interface was implemented using the C-based
-Carbon API. Starting with Emacs 23, the interface was rewritten in
-Objective-C using the Cocoa API. Meanwhile, the Carbon interface has
-been maintained independently under the name "mac".
+
+The Nextstep (NS) interface of GNU Emacs was originally written in
+1994 for NeXTSTEP systems running Emacs 19 and subsequently ported to
+OpenStep and then Rhapsody, which became Mac OS X. In 2004 it was
+adapted to GNUstep, a free OpenStep implementation, and in 2008 it was
+merged to the GNU Emacs trunk and released with Emacs 23. Around the
+same time a separate Mac-only port using the Carbon APIs and
+descending from a 2001 MacOS 8/9 port of Emacs 21 was removed. (It
+remains available externally under the name "mac".)
OVERVIEW OF COCOA AND OBJECTIVE-C