Yes of course that you can create dynamic tasks in jBPM5. In jBPM5 the human task component is a completely decoupled component that can be used also outside of the process engine context. Take a look at the following example that shows how you can create dyncamic tasks from business rules:
http://salaboy.com/2011/06/14/ad-hoc-human-tasks-for-monitoring-like-systems/
Hope it helps.. Cheers