Colonize the New World.
For exploring cellular automata like Conway's Game of Life.
A modern, cross-platform Quake game engine based on FitzQuake.
C64/Amiga emulator with shader and runAhead
3D Engine c++
Good-looking and addictive OpenSource games
A cross-platform port of Hexen II game.
GemRB is a portable open-source implementation of the Infinity Engine
4X Space Strategy Game
Multiplatform MIDI File Player for Linux, Windows, and macOS
Arianne is an engine to develop multiplayer online games like Stendhal
Cooperative multiplayer graphical RPG and adventure game
A MUD client for Android, iOS, Linux, Mac OS X and Windows
Combat Flight Simulator for LINUX. WW2. Network and VOIP. Open-source.