A: Licensing Citrix products has long required a Windows server running either Microsoft IIS or Apache. Although the resource requirements for serving up licenses aren't terribly burdensome for any existing web server, some environments might wish to keep Citrix licensing separate from other web applications.
In the old days, that separation required consuming another Windows Server license. Today, XenServer licenses can be served atop a non-Windows virtual appliance. Downloaded as a XenServer appliance in .xva format, the Citrix License Server virtual appliance delivers all your XenServer licensing needs in a streamlined appliance format.
One caution merits attention: The version currently available supports serving only XenServer licenses, which means your XenApp, XenDesktop, and other products will still require Windows. Citrix reports that an as-yet-undetermined future version of License Server will support the full range of Citrix products.