From a quick video I saw, they seem similar indeed, but I haven’t played Thrive enough. I have only made it to a single-cell prokaryotic organism, lol (which is basically very close to the beginning of the game).
The modding scene is (or, well, was) pretty active though, if you’re into that. There are still official te4 forums, but most folks hang out in the discord (yeah, I know.) including a couple old head modders that are pretty familiar with the codebase if you’re trying to do something exceptionally interesting with it.
VCMI - it’s re-written from scratch, open source, multiplatform Heroes 3 engine with many improvements and mods manager. It requires some files from the original game though.
It’s definitely a work-in-progress title, but I have really enjoyed SuperTux Advance (AGPL-3.0 according to their github page). It’s like SuperTux but with sliding, more playable characters, and more power ups. As of now it’s probably my favorite OS game at the moment. -Ace
Probably not unless you get public funding (eg, run a massive deficit, take control of the public AI to build stuff, debug features, etc) or you first create a resource chain or two to pay for transit.
OpenTTD is fantastic. The graphics might give new players pause, but if you like building networks or logistical puzzles, or just like trains, it’s still one of the best in the genre.