Are you sure you updated from the git master (fetch and merge)?
As for example:
https://github.com/krisv/jbpm/blob/master/jbpm-human-task/src/main/java/org/jbpm/task/Notification.java
Note that this has been updated to Notification_BAs, while your trace still shows:
Unsuccessful: drop table Notification_BusinessAdministrators cascade constraints
Also the PeopleAssignments class you are referencing shows table names that should be accepted by Orable DB (for example PeopleAssignments_PotOwners instead of the full name which was too long).
Kris