surprisingly there is a very similar precedent: https://en.m.wikipedia.org/wiki/Orbiter_(simulator)

something about space fight simulators perhaps

Orbiter itself is very barebones, though. Most of the content is in community addons.

And the community addons may as well not exist because nobody bothers to look for them or read the instructions for installing them.

(I may be biased though, I was an Orbiter addon project maintainer for many years)

Maybe not surprising at all. The author open-sourced Orbiter in 2021 [1]. It's MIT [2], so anyone can pick up from where he left off and create a commercial version:

[1] https://www.orbiter-forum.com/threads/orbiter-is-now-open-so...

[2] https://github.com/orbitersim/orbiter/blob/main/LICENSE

DocMart hasn't abandoned it, it's still under active development. Open-sourcing it was to get more people involved because he couldn't do everything solo anymore.

X-Plane's mostly made by one guy too, isn't it?

The computational modeling of airfoils they do in it always sounded amazing.