Do people need to create a user account in order to view the calendar?

Anybody with a user account will be able to view the calendar (according to the parameters set by an administrator for the user group they belong to).

If you want people from outside your organization to be able to view the calendar without the need to create a user account, you can turn on the Public Access option from the Manage > Integrations section and they will be able to interact with the platform as Guest users.