Business Process Management [BPM] is an issue that's been taking over my professional life. Every system I help deploy is a BPM system. 
  • Some are highly specialized, and don't allow for any Business Process design; you change your process to the tool. 
  • Some pretend to be highly specialized, but are in reality vast frameworks which allow for anything your mind desires, as long as you don't stray away from the license terms. And yes, the license is just for the specialized purpose, so if you need something different, buy another license. 
  • Some just give you a framework, an empty canvas on which to draw your process. There are limitations made in the name of usability, and you pay by workflow and user.
  • Some are open source, allow for clustering, seem to have a dual user interface, catering both to the code monkey and the flow-chart artist. 
It is this very last one I will endeavor to explore. And here's the list of BPMs, in no particular order: