NsCDE is a retro but powerful UNIX desktop environment which resembles the CDE look (and partially feel) but with a more powerful and flexible framework beneath-the-surface, more suited for 21st century unix-like and Linux systems and user requirements than original CDE.
NsCDE can be considered as a heavyweight FVWM theme on steroids, but combined with a couple other free software components and custom FVWM applications and a lot of configuration, NsCDE can be considered a lightweight hybrid desktop environment.
In other words, NsCDE is a heavy FVWM (ab)user. It consists of a set of FVWM applications and configurations, enriched with Python and Shell background drivers, couple of the additional free software tools and applications. FVWM3 is also supported.