Surely POSIX is the least of it. Mac apps are built on an API that has been much extended since the NeXT days and which even then was a complete wrapper over th

Surely POSIX is the least of it. Mac apps are built on an API that has been much extended since the NeXT days and which even then was a complete wrapper over the underlying Unix OS. Think "copying QT and the whole KDE ecosystem" to get a grasp of the scale of it.