Orx: Portable Game Engine
Open source reimplementation of GTA San Andreas game engine in Unity
Godot backend for video games based on Valor TTRPG
A free 3D game engine to create games and realtimes scenes for Windows
Opensource crossplatform Fallout 2 game engine writen in C++ and SDL
An isometric arcade-style game of skill, puzzles and exploration
A modern, cross-platform Quake game engine based on FitzQuake.
Portable version of the incredible Godot Game Engine
Full featured MUD server with all the trimmings.
Cross-platform 2D game engine (+ full OpenGL, +full OpenGL ES )
C++ lightweight cross-platform game engine
Pycraft is an open-source, OpenGL based game made in Python
Old-school 2D game engine
3D Scene Builder
Amateur 3D Game Engine
A game engine for console based text games
SDL based generic 2D game engine
Vivid3D is an open-source 3D engine with powerful 2D UI.
A Tile-based Game Engine written in C# mimicing retro consoles.
Game framework with AI
A simple cross-platform game engine for creating old-school 2D games