Camunda - The Universal Process Orchestrator
jBPM - jBPM is a flexible Business Process Management (BPM) Suite.
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.
Imixs-Workflow - Imixs Workflow is a BPM Framework with the goal to reduce the complexity of business applications.
Drools - Drools introduces the Business Logic integration Platform which provides a unified and integrated platform for Rules, Workflow and Event Processing.
Pega - Pega provides business process and customer relationship management solutions for organizations.