I found this on Solitarian's channel, on his latest stream episode(11 September 2022):
Commenter: is this abandoned?
Solitarian: The game? Yes. Both of the developers are no longer working on it. The game was a one-man show for a long time, and eventually that situation ended and the thing was de facto dead.
Commenter: sad to hear, as someone who wants to play / build a simulator myself, could you inform me of the main causes of failure? is it the performance costs of such a simulation, lack of market, etc? To what degree is the source code open-sourced so we can learn from it? Thanks in advance.
Solitarian:
There were two developers. One had a family and full-time job and just quit working on the project because his responsibilities elsewhere were more important. The other developer was doing all the work while not getting enough money for it to get by, so he got a full-time job. There also came a point where a lot had been developed, but then developer #1 came back briefly and didn't like it, so a big chunk of it was just removed. That disappointed developer #2 and both realized that the situation was not tenable and stopped the project.
As far as open-source stuff goes, I do not know. You'd have to ask the developers that. I think their Discord server is still active.