Aventis Systems offers user and device Client Access Licenses (CALs) for Windows Server 2012. A Client Access License (CAL) is required for each employee, or each employee device, that accesses a Windows Server installation.
Windows Server CALs can be used in one of two licensing modes: per user/per device or per server. This designation is determined at the time you install your Windows Server product. The CAL themselves do not have a specific mode designation.