Odamex is a free, cross-platform, modern client-server Doom engine
0 A.D. is a free, open-source, cross-platform real-time strategy game.
A fun realistic multiplayer free-and-open-source first-person-shooter!
A free 3d game for PC that does not limit the player. Fight,Build,Gain
GameServer is a sophisticated, game server designed for online games
FiveM (GTA: V, Grand Theft Auto V Multiplayer) utilities
mGSTEP port of the Cube game engine
FreeCS is a free-software reimplementation of Counter-Strike 1.5.
Suite of utilities to make running a Lugdunon server easier
NOOBS compatible distro image for wrapper around the XLink Kai Engine
This lets you create worlds more easily and to recreate a world
Makes running a PSO server on Linux easier
Set of utilities for making Xpilot easier to operate
C/C++ , PHP, PYTHON, 3D ENGINES, CHROME NATIVE CLIENT
starrydb is game server engine
PvP, MUD RPG.
A collection of all maps and games made for the TripleA game engine
Java decentralized cross-platform network multiplayer game engine
A maintenance toolbox for cleaning up Space Engineers saves.
Free strategy browsergame engine.
Your death sentence awaits...
3D FPS Digital Paintball 3 Multiplayer Online Game
Library for creating turn-based games with simultaneous moves.