In general, I would say yes, it is possible. But it all depends on what you would like to use as viewer. By default jBPM uses console and I think there is an eclipse test client for human tasks as well.
So if you would like to have it integrated with console you should write plugin (if I recall properly implementation of FormDispatcherPlugin), something similar to the jbpm-gwt-form.
But if you like to have it stand alone you would need to leverage both REST interface and Task Service client to connect to task service to operate on tasks. By default jBPM console is responsible for retrieving task forms, but if you like to use JSF for that, you won't need that any more.
michael gantenbein wrote:
How can I get and set variables in my process programmatically?
To remotely access variables you could use REST interface, there is a process management facade that lets you, among other functions, set/get variables for particular process instance. For access it directly you should get variable scope from process instance and next add/retrieve variables out of it.
HTH