FHEM - FHEM (TM) is a GPL'd perl server for house automation.
Home-Assistant.io - Home Assistant is an open-source home automation platform running on Python 3.
pimatic - Home automation framework that runs on node.js.
Homebridge.io - Homebridge is a lightweight NodeJS server you can run on your network that emulates the iOS HomeKit...
openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation
ioBroker - flexible and modular application for the IoT and Smarthome