The flexible game engine
An OpenGL RTS game engine written in C
Xash3D FWGS engine
3D game engine/framework in C, with Luajit and Python bindings now
The ioquake3 community effort to continue supporting/developing id's
An iOS & tvOS Frontend for Multiple Emulators
A free/open source client and automation tool for Ragnarok Online
Go bindings for raylib, a simple and easy-to-use library
Orx: Portable Game Engine
A free and open-source Touhou Project fangame
Cooperative multiplayer graphical RPG and adventure game
A modern, cross-platform Quake game engine based on FitzQuake.
SDL based generic 2D game engine
0 A.D. is a free, open-source, cross-platform real-time strategy game.
A cross-platform port of Hexen II game.
A Wii-like game that can be controlled using a Nunchuk or a phone.
A free 3d game for PC that does not limit the player. Fight,Build,Gain
A fun realistic multiplayer free-and-open-source first-person-shooter!
Open source FPS/RTS Game
A 16 bit style game on the 16-bit IBM XT.
A completely free, open-source, 2D game engine