Licensing Windows Server

Microsoft’s only server OS, Windows Server, contains myriad capabilities necessary for building and maintaining a network infrastructure, such as directory services and administration tools. It is also the OS platform on which all Microsoft server-based applications are built.

Windows Server generally requires a license for the server and Client Access Licenses (CALs) for each client user or device that accesses the server. External Connectors are available for users outside the organization licensing the server, such as customers. However, OS server licenses come in several editions, and the precise licensing model and rights granted vary by edition—especially related to hardware virtualization. (Hardware virtualization makes it possible for multiple, different OSs to run simultaneously on a computer, each in its own virtual machine that emulates a complete computer in software.) Two server features, Terminal Services and Rights Management Services, also require their own CALs.

Licensing Windows Server for use within an organization is generally straightforward if hardware virtualization is used sparingly—a Standard or Enterprise Edition server license is acquired for each physical server machine and one Windows Server CAL is purchased for each user or device within the organization. However, accommodating scenarios involving nonemployees or making heavy use of virtualization complicates Windows Server licensing considerably.