You'd have to do a separate install for the other group. If you are going to be using the same database, you'd have to edit the config.inc.php to change the table name. By default it is set to epc_calendar. Once you've changed the table name, then you can complete the setup for the second install by running the setupSQL.php link.
As for the licensing, you have to think of it as paper calendar replacement. If your events would go on separate paper calendars, then you should buy a second license.
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