BYOND - BYOND is the premier community for making and playing online multiplayer games.
Cyberix3D - Free online 3D Game Maker. Make your own 3D games online!
Defold Engine - Defold lets you quickly build high performing, cross-platform games together with your team.
Open 3D Engine - Open 3D Engine is an open-source 3D game development engine in real-time.
ct.js - ct.js is a 2D game editor (desktop app) based on web technologies.
Castle Game Engine - An open-source 3D/2D game engine for ObjectPascal.