Microsoft Lync Server 2013 Plus user CAL through the Microsoft Open Government Program. IMPORTANT NOTE:
Microsoft Lync is a unified communications platform on which users can make a phone call keep track of their contacts' availability send an IM and start or join an audio video or web conference.
For Lync Server access to Enterprise voice workloads are licensed through the Lync Server Plus CAL. Enterprise voice capabilities previously available through the OCS Enterprise CAL are now only available through the Lync Server Plus CAL. Like the Enterprise CAL the Plus CAL is an additive CAL and can only be purchased once the Lync Server Standard CAL has been acquired.
A server license and a minimum of 5 CALs are required. Lync Server Plus requires a Standard CAL for every Plus CAL.