NsCDE and other CDE lookalikes seem to have a thicker horizontal bar in the upper left decoration than this and the original CDE, but perhaps that is one of the customizations the author mentions.
Also, the background seems to be from Elementary OS beta. Specifically, blueprint hue shifted to match purpleprint, based on the cropping and vignette.
Thank you for the info! I wasn't aware of the X11 colors.
The original author only gives this information about their setup:
I imagine this is not Motif since it's a GTK theme? Not very familiar with GUI stuff.
Maybe it's FVWM? It is a derivative of TWM.
Perhaps NsCDE?
NsCDE and other CDE lookalikes seem to have a thicker horizontal bar in the upper left decoration than this and the original CDE, but perhaps that is one of the customizations the author mentions.
Also, the background seems to be from Elementary OS beta. Specifically, blueprint hue shifted to match purpleprint, based on the cropping and vignette.