The code might still be a derivative work.

The first thing that crossed my mind is that they might try to cancel OpenTTD. Chris Sawyer reportedly wasn’t too happy about OpenTTD but didn’t too much against it, maybe recognising that it is a fan tribute. Nobody can expect that of Ataris’s corporate lawyers.

Giga Romania? Does it contain Hungary? /s

I mean, it’s commendable they are still making updates. But there is a lot of stuff thats still not OK after all those years and probably won’t ever be. The cars require low server load and OK connection, otherwise you can still get the Laika experience. Also no helicopters apart from some mods. But the zombies were mostly OK last time I played.

I take it you haven’t bought DayZ in early access.

Perhaps look into Space Engineers in creative mode? Although you can’t “build” the terrain and it does have it’s own sci-fi art style.