[Blahagun]

Not really. Although there are of course similarities, NeXTSTEP as a graphical interface was implemented from the ground up by NeXT (Jobs' new computer company after he left Apple). The GUI of almost all other commercial UNIX operating systems was developed with the Motif toolkit and there was a whole desktop environment - Common Desktop Environment - which was popular for some time. Motif wasn't free though, so new GUI toolkits were being developed, most of them free, like GTK (initially for building the GIMP UI), and desktop environments were being created on top of them like GNOME. Because they were free and feature rich, Motif and CDE started declining and that's why you don't see them anymore as GUIs on UNIX based OSes. Then Apple bought NeXT and redesigned NeXTSTEP's UI and called it MacOS X.