openHAB - "empowering the smart home" - vendor and technology agnostic open source home automation
ioBroker - flexible and modular application for the IoT and Smarthome
Home-Assistant.io - Home Assistant is an open-source home automation platform running on Python 3.
Domoticz - Domoticz is a lightweight Home Automation System
SEQUEmatic - SEQUEmatic lets you build sequences to link together your various smart devices.
Homebridge.io - Homebridge is a lightweight NodeJS server you can run on your network that emulates the iOS HomeKit...