Each person that needs to create or edit the calendar will need a license. The current version will allow a shared file to be placed on the server and shared among the group. This file can be viewed simultaneously but only one person at a time can edit it.
The software does provide notifications when the file has been updated as well as when the file is locked for editing. You can also have multiple people work within their own calendars which will avoid the simultaneous editing issue. You can then easily combine these and publish them as PDF or via a web calendar as well. Which method works best for you will depend on your situation.
We do provide volume discounts that start at two units and increase per unit. The online store will automatically calculate discount for you based on units or submit a volume pricing request.