Publisher's description of BusySync

From BusyMac:

BusySync is a Mac OS X System Preference Pane that runs in the background and adds calendar sharing and syncing capabilities to iCal. BusySync lets you sync iCal with Google Calendar and share calendars with other users on your LAN or the internet without the need for a dedicated server. Shared calendars can be viewed and edited by multiple users and changes are instantly synchronized with all users on the network and/or with Google Calendar. You can even make changes to shared calendars while offline and your changes will sync when you reconnect to the network.

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