Hi Fernando,
I think that you can meet those requirements with jBPM5 but as you may notice we are using the BPMN 2.0 modeling notation to define our processes and activities and its important for you to define which type of activities you are planning to run in parallel. Are all automated activities? are all asynchrnous activities? are all blocks of code that needs to be executed by the process itself? if you can elaborate on that we can guide you on the implementation.
Cheers