Well to start up human task using ant, all you need to run is start.h2 before it. Or the target data base server should be runnning in case you have migrated it to another db.
If you run the ant scripts in the sequence
ant start.h2
ant start.jboss
ant start.human.task
ant start.eclipse
Then I believe you will get a conflict with the address:port usage as the script ant start.jboss has already started task service. I dont remember correctly but If I am not wrong, in the very first draft of jbpm 5, task service was required to start up this way. STarting up jboss did not start human task service with that version. And quite a lot of documentation has not been modified with the upgrades. I am not sure about it though.
Well All you need to do is
ant start.h2
ant start.human.task
Regards.