"Unlike Shakespeare's rose, Xen, by any other name, is most
definitely not Xen, and 'Xen' trademark holder XenSource Inc. has
told other virtualization players that unless they agree to its
trademark terms, to stop calling their products as such.
"XenSource, the commercial entity founded by of the University
of Cambridge researchers that developed the open source hypervisor,
made the Xen community aware of their trademark policy this fall,
and, so far, at least one vendor--Virtual Iron Software Inc.--has
agreed to stop using the name..."