in what way is this integrated?

What can drupal do with web calendar? Is it a menu-call-back page with a single sign on? Is it connected to blogs or any content type? Can each drupal user have it's own calendar? can another user or role modify another person's calendar? Will other drupal modules and filters (such as TinyMCE and BBCode) have the ability to modify output?

The actual module consists of
- a menu call-back page that displays webcal in a iframe
- some settings for controlling how the iframe is displayed
- some permissions you can set

However some plugins for WebCalendar are provided with the module which allow WebCalendar to authenticate directly against the Drupal database. All user management is done via Drupal.

When you logn to your Drupal site, WebCalendar will recognise you as logged in (so yes single sign on).

WebCalendar is not connected to any content types, blogs, modules, filters. It is simply displayed in an iframe.

By setting permissions you can determine if users can login to WebCalendar as a unique user (if WebCalendar is setup correctly, they will get their own calendars), and if they are able to view the public calendar. Whether or not a user can modify another users calendar is controlled by settings in the WebCalendar application itself.