>>2019
it's not an exact clone of anything. I'd tried CDE, or at least a port of CDE, on my machine, but it felt clunky. This was some time ago so I may not remember correctly but a lot of the older interfaces I tried, including a port of the IRIX desktop environment, seem to be pretty mouse-heavy. A lot of point and click to launch things which I don't like. Maybe I just didn't know how to use or configure them properly.
Even on Windows, I like to launch a program by hitting the Windows key which opens up the Start menu, then typing the first few letters of the program and hitting return.
I have a couple taskbar icons for my email client and my main web browser but everything else is launched from the start menu. For example, if I want to launch VirtualBox, I hit the Windows key, type "virt" and hit enter.
For Seamonkey: Win + "seam" + return
For DOSBox: Win + "dosb" + return
So anyway that's why I didn't settle on some of the other UNIX desktop environments. I can't remember which other one I tried. I also don't like Windowmaker and some of the very barebones window managers, either. They also feel inefficient.
I use XFCE. All I've done is change icon packs--you can find icons packs with some digging that'll replicate IRIX, NeXTStep, etc.I changed theming options and installed ports of old UNIX programs. (Such as fsv and xosview).
The icon theme I had last I checked was called "Iris", the window manager theme is cdetheme_solaris, and the GTK theme was something called belle pintos grande which I believe might translate to something obscene in Spanish, but that's what I'm using.
I remember it took a bit of work to find the specific themes and icons but basically it lets me make XFCE, which I find very usable, look the way I want it to look.