This product comes pre-bundled with the server license and 25 CALs. If you need additional CALs, you may order them seperately.

Windows Server 2003 R2 Enterprise Server License differs from Windows Server 2003 R2 Standard Edition primarily in its support for high-performance servers and its ability to cluster servers for greater load handling. These capabilities provide reliability that helps ensure systems remain available even if problems arise. With Windows Server 2003 R2 Enterprise Edition, organizations can deploy highly available and scalable applications on industry-standard PC hardware. The result is a highly productive infrastructure optimized for running all your business-critical applications and services. For example, Windows Server 2003 R2 Enterprise Edition excels at supporting networking, messaging, inventory and customer service systems; databases; e-commerce Web sites; and file and print servers. For growing organizations, the ability to scale critical applications both up and out allows them to meet changing demands. Regardless of the size of your organization, Windows Server 2003 R2 Enterprise Edition is a good choice for running applications that must be available at all times.

Licensing
A Server License is required for each operating system environment running Windows Server 2003. A User/Device CAL is required when a user or device is directly or indirectly accessing a Windows server. Additionally, if the user or device is accessing or using the Remote Desktop Services functionality of Windows Server, a Remote Desktop Services CAL is also required. This product comes pre-bundled with 25 CALs. You can order additional CALs, if needed.