Open Source C Game Engines

QuakeSpasm is a *Nix friendly Quake Engine based on the SDL port of the popular FitzQuake. It includes some new features, important fixes, and aims for portability and 64 bit correctness.

A portable game engine for classic first person shooters such as DOOM, Heretic and Hexen. Lets you enjoy the original games using modern technology, including high-resolution OpenGL graphics, 3D models, and dynamic lighting effects.

3D game framework in C, with Luajit and Python bindings now.

Aleph One is the open source continuation of Bungie's Marathon 2 FPS game engine. Aleph One plays Marathon, Marathon 2, Marathon Infinity, and 3rd-party content on a wide array of platforms, with (optional) OpenGL rendering, Internet play, Lua scripting, and more.

Smokin' Guns is a GPLv2 licensed first person Western style shooter based on the Quake 3 engine (Id Tech 3) developed by a loosely knit team of developers and artists. This project represents the game engine.

Haxima is an Ultima-like game engine (2D tile graphics) with combat, magic, NPC AI, an embedded scripting language, and in-game editing.

OpenMoHAA is a game engine that is compatible with Medal of Honor: Allied Assault media and network protocol, based on the ioquake3 project.

Pipmak is a cross-platform game engine and authoring environment for point-and-click adventure games in the style of the Myst series. It supports panoramic nodes and uses Lua for scripting.

Orx is a portable, lightweight, plugin-based, data-driven and extremely easy to use 2D-oriented game engine. As orx is data driven, it allows users to create games with a small number of lines of code and reduces drastically the development time.

Action/RPG Game Engine. Overall game engine is to be open source, but not the art assets.

A platform independent 2d game programming framework for c/c++ programmers with least possible dependencies for easy porting and with focus on easy api calls and the requirement of commercial programmers

Terra Tenebrae is a free (as freedom) multi-Players RPG game engine based on client/server technology. The assets used are in licenses CC0, CC-by, CC-by-sa or GPL.

WFIRE is a low-level game engine which provides a portable library allowing for writing video games for multiple classic targets. Originally written for a game called the Crypts of Eldor, WFIRE aims to provide compatibility with a number of constrained environments, such as DOS and the Amiga. It also aims for "new-retro" computers such as the Commander X16 and the Neon816. Of course, modern operating environments such as Windows NT and GNU/Linux are also planned. WFIRE is meant to reduce the effort of writing your own game engine by providing a common framework for functions such as rendering, sound output, and display management.