Imixs-Workflow - Imixs Workflow is a BPM Framework with the goal to reduce the complexity of business applications.
Camunda - The Universal Process Orchestrator
ProcessMaker - ProcessMaker is an easy to use BPM and workflow software solution. It is used to design, automate, and deploy business processes of any kind.
Bizagi - Bizagi is a Business Process Management (BPMS) solution for faster and flexible process automation. It's powerful yet intuitive BPM Suite is designed to make your business more agile.
Kissflow - Kissflow is a workflow tool & business process workflow management software to automate your workflow process. Rated #1 cloud workflow software in Google Apps Marketplace.
Celonis - Celonis offers process mining tool for analyzing & visualizing business processes.