n8n is a free and open fair-code licensed node based Workflow Automation Tool to easily automate your tasks across different services. You can self-host n8n, easily extend it, and even use it with internal tools.
Beehive is an open source event and agent system, which allows you to create your own agents that perform automated tasks triggered by events and filters. It is modular, flexible and really easy to extend for anyone. It has modules to interface with, talk to, or retrieve information from Twitter, Tumblr, Email, IRC, Jabber, RSS, Jenkins, Hue etc.
Project Flogo is an open source, resource efficient, Go-based ecosystem for building event-driven apps. It is designed to abstract the event processing paradigm from event consumption enabling devs to build once, consume from anywhere and process using any of the supported actions.