Customers of the Cisco CallManager software are required to purchase a CallManager Client Access License (CAL) for each IP phone, SoftPhone or other endpoint device or application (IP phone) that registers with the CallManager software. This CAL requisite applies regardless of the source (Cisco or a third party) or the functionality of that IP phone.
Customers who purchase a spare IP phone need not purchase a CAL for that spare if that spare is used to replace another IP phone for which a CAL has already been paid.
Note: That spare phone will never be registered with a Cisco CallManager until the phone that it replaces has been de-registered with that CallManager.
If the spare IP phone is not used as a replacement for an IP phone for which a CAL has already been paid, the customer must purchase a CAL for that spare. Cisco CallManager CAL policy is that customers must purchase a matching number of IP phones and associated CALs, with the exception of spares used as replacements.
http://www.cisco.com/en/US/products/hw/phones/ps379/products_qanda_item09186a00800a6763.shtml#q37
