Eclipse Origins!

PlayCanvas is the world’s easiest to use WebGL Game Engine. It’s free, it’s open source and it’s backed by amazing developer tools.

Erebus is an Open Source RPG (Role-Playing Game), for PCs, smartphones, tablets and handhelds.

Lips of Suna is a tongue-in-cheek action RPG. It's an open world game that focuses on action heavy and versatile gameplay, dynamically changing game world and ease of customization and modding.

Spring is a versatile 3D RTS game engine. Using extensively Lua for scripting game-specific code to make nearly every aspect of the engine customizable, from GUI, to unit AI, to pathfinding.

The Flexible Isometric Free Engine (FIFE) is an open source, cross-platform game engine written in C++ with Python scripting abilities. Inspired by the isometric view found on Fallout and Fallout 2, it can nonetheless be used to create about any 2D game, as the flexible on the name implies. The non-tridimensional approach ensure FIFE games can run on less powerful hardware, and also simplifies framework programming and content creation.

Battlegrounds: RPG Edition (aka BRPG) is virtual tabletop software designed to enhance your pen-and-paper roleplaying games, whether your players are in the same room, or on the other side of the world.

EpicTable is a virtual tabletop (sometimes referred to as a “VT”) that allows you and your friends to play your favorite pen-and-paper roleplaying games, regardless of whether you’re sitting across the table or across the world from one another.