Before version 3.0 you can only attach one user and one category to an event.
To add more users to an event you would have to create a N:M relation from the event to the users (or M:N) in the database. That solves the issue.Â
However, the bean allows only unique eventid.
Therefore you must return the PK of the N:M table to the Calendar bean to make the eventid unique and all (under water the same) appointments show up for different users.
IMPORTANT: To edit, update or delete the event you need to retrieve the actual eventid via the N:M table to take care of the fact that the PK of the N:m table is not the eventid itself.