Looking at that screenshot, even though I've been a very happy KDE user for many years now, I do kinda miss the days when many Xfree86 desktop environments were influenced more by NeXTStep than Windows.
Thanks, I spent a couple of hours playing around with that. It didn't work quite right but still I've got some glorious retro ugliness going on. A mishmash of CDE, Windows 2000 icons and KDE 5, it's mental and I love it.
The Motif look, what we are looking at here, is driven by the same UI guidelines that early Windows and OS/2 followed. You will notice a lot of similarity between them.