Xlibre it's not needed when Xenocara does a better job.

Huh. I was going to question whether that was even possible, but apparently https://github.com/marchaesen/vcxsrv , http://www.straightrunning.com/XmingNotes/ , and https://x.cygwin.com/ are all based on Xorg, so I guess if you wanted you could likely get Xlibre to build for Windows. But... Why? CDE isn't really something that makes sense nested inside another system, and AFAIK modern Windows is pretty hostile to replacing DWM (or wherever their GUI is these days).

I am mostly interested in using Windows as a dev platform for revitalizing old Motif programs.

Unless the point is about FOSS, I had no issues using Hummingbird Exceed back in the CDE glory days.