Scratch - Scratch is the programming language & online community where young people create stories, games, & animations.
Cyberix3D - Free online 3D Game Maker. Make your own 3D games online!
Tynker - Game Worlds for Kids to Learn Programming
Godot Engine - Feature-packed 2D and 3D open source game engine.
RoboGarden - RoboGarden provides a complete, game-based suite that teaches coding from beginner to professional level, starting with block programming and progressing to professional Python and JavaScript programming.
Open 3D Engine - Open 3D Engine is an open-source 3D game development engine in real-time.