(I'm an active-ish member of the GNUstep list & in my spare time I've been working on a remix of openSUSE with GNUstep on top; I exchange messages with ProBono about UI design, history, keyboard layouts etc.)
The initial version of the HelloSystem was based on GNUstep on FuryBSD. However, apparently -- I did not see any of the comms -- he found the GNUstep people very hard to work with and fairly quickly ditched it and started to roll his own.
I must say that I've found the GNUstep folks to be rather intransigent myself. I've found it hard to get answers to simple questions, and when I make small suggestions, they've been mostly been shouted down or ignored.
ISTM that the GNUstep project see themselves as building a set of libraries, classes, and tools for building apps. As it happens, as a side-effect of that, they've built a desktop environment as well, but they are not interested in that and don't care about it. Desktops are not their business. They're perfectly happy if others want to use GNUstep to build desktops, though.
For reasons that escape me, the GNUstep team are not bothered about ensuring that there are current packages in mainstream Linux distros. This seems to be seen as something for others to do.
Etoile violated one of the core rules of FOSS, ISTM: "release early, release often." They never actually put out a release at all in some 15 years of work. You want code? Here's the source: download it and build it yourself. It's a tragic oversight.