Camunda - The Universal Process Orchestrator
OutSystems - Build Enterprise-Grade Apps Fast.
jBPM - jBPM is a flexible Business Process Management (BPM) Suite.
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.
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.
Zoho Creator - Zoho Creator is a low-code application development platform that helps you build a custom, mobile-ready apps to run your business.