Home-Assistant.io - Home Assistant is an open-source home automation platform running on Python 3.
Raspberry Pi - The Raspberry Pi is a tiny and affordable computer that you can use to learn programming through fun, practical projects. Join the global Raspberry Pi community.
ioBroker - flexible and modular application for the IoT and Smarthome
Orange Pi - It’s an open-source single-board computer. It can run Android 4.
openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation
Odroid - The Odroid is a series of single-board computers and tablet computers created by Hardkernel Co.