DOSBox Staging is a modern continuation of DOSBox
3D Procedural Game Engine Using OpenGL
VR Mosaic - C++ Builder Applet v.2.5
An implementation of the popular Sokoban puzzle game. Win/Mac/Linux
Vivid is a modern C++ 3D engine using OpenGL4+
3D Game engine with editor
Quake C mods and support - SSQC / CSQC
Cross-platform port of Arx Fatalis, a first-person role-playing game
1st 3D game engine built in C# for .NET, Visual3D Engine's predecessor