Server Licenses: A license must be assigned for each instance of the server software that is running the front-end server role—all other roles do not require a license. Lync Server 2013 is licensed in one edition for all deployment scenarios.
Client Access Licenses (CALs): To access the Lync Server 2013 services, a Client Access License is required. Three CALs are available for Lync Server:
Enterprise CALs and Plus CALs are additive to the Standard CAL. CALs are available as either Device CALs or User CALs.
User Subscription Licenses (USLs): Two USLs are associated with Office 365 and Lync Online. Plan 1-provides Presence, IM, peer-to-peer VoIP/Video, and Skype Connectivity; Plan 2 adds Lync Meetings capability.
Client License: Lync 2013 client licensed via Office Professional Plus (and is also available as a standalone). Lync Windows 8 client is licensed via Windows Store and other mobile clients are available via the relevant platform store. Lync Basic 2013 client licensed via download from Microsoft.
Download the Lync Pricing and Licensing Guide