MiniZinc - MiniZinc is a free and open-source constraint modeling language.
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.
OptaPlanner - Mathematical optimization software
Pipefy - Pipefy is a process management software that empowers anyone to create and automate efficient workflows on their own without code.
Higson.io - Hyperon is a BRMS, that was created with very large decisions and hyper-performance in mind. It stands out with the concept of the business domain which organizes the whole configuration in easy to manage way.
Process Street - Create beautiful rich process documents in a simple to follow checklist format. Fast, free and incredibly simple to use.