Home-Assistant.io - Home Assistant is an open-source home automation platform running on Python 3.
Unity - The multiplatform game creation tools for everyone.
ioBroker - flexible and modular application for the IoT and Smarthome
Godot Engine - Feature-packed 2D and 3D open source game engine.
openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation
Blender - Blender is the open source, cross platform suite of tools for 3D creation.