Microsoft offers several flexible licensing options that allow you to scale Lync to your business’s specific Unified Communications needs.
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:

- Lync Standard CAL (to use IM, presence, one-to-one audio, and video; Skype Connectivity)
- Lync Enterprise CAL (to use meetings - audio, video, and web conferencing)
- Lync Plus CAL (to use enterprise voice features)

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 and Video, and Plan 2 adds Lync Meetings capability.