Appcelerator Titanium - Appcelerator Open Source
Unity - The multiplatform game creation tools for everyone.
React Native - A framework for building native apps with React
Godot Engine - Feature-packed 2D and 3D open source game engine.
Onsen UI - HTML5 Hybrid Mobile App UI Framework - work with Angular, React, Vue, Meteor & pure JavaScript. Material & Flat design.
Blender - Blender is the open source, cross platform suite of tools for 3D creation.