One great Open Source game that comes to mind is definitely VVVVVV. - https://thelettervsixtim.es. - Source: Hacker News / about 2 years ago

{ "id": 0, "name": "Captain Viridian from VVVVVV", "description": "A miniature 6x6 art of Captain Viridian, the main character from the indie platformer VVVVVV. The art was built and maintained by 3 VVVVVV fans after this area was recovering from the void.", "website": "https://thelettervsixtim.es/", "subreddit": "", "center": [ 1060.5, 1655.5 ], "path": [ [ ... Source: about 2 years ago

The official website is actually https://thelettervsixtim.es so there you go. Source: over 2 years ago

I think the game website was http://thelettervsixtim.es. Source: over 2 years ago

Well how about I introduce you to... FreeCiv! https://freeciv.org/. - Source: Hacker News / 7 months ago

There are many other commercial projects similar to this (colonist.io landover.io etc). None of them are open source though. This has been done in the past extensively (see freeciv.org, or Terasology, or 0 AD etc). Source: 8 months ago

While many CivFanatics have probably heard of FreeCiv and Civ2Clone, there is also another freely available opensource indie game inspired by Civilization 2 called C-evo! C-evo aims to recreate the classic mid 90s TBS Civ2 like experience, but with more emphasis on a custom military unit designer, extremely powerful/deadly AI, and careful design of the rules, resulting in a true challenge. The game uses similar... Source: 8 months ago

FreeCiv uses its own FOSS engine[0], can keep you occupied for days. [0] http://freeciv.org/. - Source: Hacker News / 8 months ago

The client and server are separate binaries; they are released together on freeciv.org, but Linux distributions put them into different packages. Source: almost 1 year ago