Hi TC,
I'm in charge of writing those docs, but I'm still working on unifying all these classes, if you take a look on master those classes are deprecated now. I will be writing in the following weeks these documents which will include the specification of a new set of WorkItemHandlers for Human Tasks. You can take a look a these classes in github. They are called:
AbstractHTWorkItemHandler -> GenericHTWorkItemHandler & AsyncGenericHTWorkItemHandler -> Then the concrete implementation for the different transports: HornetQHTWorkItemHandler and Mina...
Cheers