What are some alternatives?
When comparing ProActive Workflows & Scheduling and StackStorm, you can also consider the following products
Metaflow - Framework for real-life data science; build, improve, and operate end-to-end workflows.
RunDeck - RunDeck is an open source automation service with a web console, command line tools and a WebAPI.
Luigi - Luigi is a Python module that helps you build complex pipelines of batch jobs.
Pipedream - Integration platform for developers
Parabola - Automate manual processes without spreadsheets or code
Apache Oozie - Apache Oozie Workflow Scheduler for Hadoop