openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation
Home-Assistant.io - Home Assistant is an open-source home automation platform running on Python 3.
ioBroker - flexible and modular application for the IoT and Smarthome
IP-Symcon - IP-Symcon is the innovative centre of your entire building automation!
FHEM - FHEM (TM) is a GPL'd perl server for house automation.
Home - Securely control all your HomeKit accessories from your favorite iOS device.