Computer Configuration > Policies > Centrify Settings > Mac OS X Settings > Firewall > Enable iTunes Music Sharing
Enabling this group policy is the same as clicking the On checkbox to allow communication through the firewall for iTunes Music Sharing.
On Mac OS X Servers, enabling this policy has no effect. If the firewall is enabled, the iTunes Music Sharing service is not allowed through the firewall.
If you do not enable this group policy, traffic for iTunes Music Sharing will be blocked from the local computer. Users will be able to access iTunes collections on other computers, but the local computer cannot be used to serve any iTunes collections.
This policy can take effect dynamically at the next group policy refresh interval without rebooting the computer.