From Platinum Arts:
Platinum Arts Sandbox is an open source easy to use free 3D Game Maker and 3D World Creation program currently used in many schools throughout the world that allows kids and adults to create their own video games, worlds, levels, adventures and quests, even cooperatively. The goal is to make it accessible to kids but also powerful enough for full game projects. With a simple click and roll of a mouse wheel users can modify the world however they want. In the words of Meg, a nine year old Sandbox whiz "Press Edit and go fulfill your dreams!". Now features new game modes such as sidescroller, machinima, kartmode, RPG, and more. Version 2.3 includes unspecified updates.
What's new in this version:
Version 2.3 includes unspecified updates.