With more than 150 monsters, about 3000 maps to explore, 13 races, 15 character classes, a system of skills, and many artifacts and treasures, this cooperative multiplayer graphical RPG and adventure game puts you in an elaborate, magical world. However, the graphics and game play are decidedly retro. Operating System: Windows, Linux, OS X.
For those who like their games really old-school, Dungeon Crawl is similar to the old DOS game Rogue. You must maneuver your way through an underground maze to retrieve the Orb of Zot while defeating various monsters and overcoming other obstacles. Operating System: Windows, Linux, OS X.
This MMORPG is set 2000 years in the future on the world of Atys. The source code is available and it's free to play, but you'll need a subscription if you want to advance past level 125. Operating System: Windows, Linux, OS X.
Like many of the best commercial flight simulators, FlightGear offers a very realistic flying experience with more than 20,000 real-world airports. It offers multiple types of aircraft with extremely accurate controls and operation. Operating System: Windows, Linux, OS X, others.
48. LinCity NG
As you might guess from the name, this is an open source version of SimCity. (The "NG" version is an update of the older LinCity game.) To win, build up your city to create a sustainable economy or evacuate all of the population on spaceships. Operating System: Windows, Linux, OS X.
Based on the original code for SimCity, Micropolis offers the familiar city-building scenario with somewhat dated graphics. It's also part of the One Laptop Per Child project. Operating System: Linux, Unix.
Inspired by the game Elite, Oolite is a single-player space simulator that requires you to pilot ships around the universe, creating space stations around inhabited planets. Along the way, you'll need to fight off enemy ships. Operating System: Windows, Linux, OS X.
Inspired by the open source project FreeReign, OpenCity is another city development simulator. It also uses a lot of concepts from SimCity2000, although it isn't a clone of that game. Operating System: Windows, Linux, OS X.
This clone of Transport Tycoon Deluxe adds a number of features not found in the original commercial game, including multi-player games for up to 255 players. As in the original, the goal is to make a lot of money transporting passengers and freight by land, water and air. Operating System: Windows, Linux, OS X.
53. Rigs of Rods
Extremely popular, Rigs of Rods is a vehicle simulator that uses a soft-body physics engine to provide very accurate simulations. In order to run it, you will need a fairly up-to-date system. Operating System: Windows, Linux, OS X.
Similar to Transport Tycoon Deluxe and OpenTTD, this app allows you to build up a city full of a variety of transportation networks. Just stay out of debt, or your game will soon be over. Operating System: Windows, Linux, OS X.
55. Vega Strike
Vega Strike describes itself as a "3D action-space-sim that lets you trade, fight, and explore in a vast universe." It's a beta release but very playable, and the graphics are very good. Operating System: Windows, Linux, OS X.
56. 0 A.D.
Now in its sixth alpha release, 0 A.D. looks and feels a lot like Microsoft's Age of Empires series. The high-quality graphics are particularly noteworthy, and we assume the game will continue to improve and eventually enter beta and general release status. Operating System: Linux, Windows, OS X.
Created "in the tradition of the Battle Isle series," Advanced Strategic Command is a turn-based strategy game where combat units fight it out on a map made of hexagonal spaces. It offers both single- and multi-player play. Operating System: Linux, Windows.
This turn-based strategy game is set in a high-fantasy world full of elves, necromancers, orcs and warriors. It includes multiple scenarios for gameplay or you can play against up to eight other people in multiplayer battles. Operating System: Linux, Windows, OS X, iOS.
Set in a futuristic world, BosWars is a real-time strategy game where you must build up your economy and your military at the same time. You can play alone or connect to other opponents over a LAN or over the Internet. Operating System: Windows, Linux, BSD, OS X.