Xen.org, the community which develops the Xen hypervisor under the GNU General Public License (GPLv2) has released version 4.1, this version is the follow-up of version 4.0 which was released in April last year.
Xen is a virtualization engine, used by several Linux distributions, NetBSD and Solaris but also serves as a basis for the Xen Cloud Platform (XCP) and Xen Hypervisor for Client Devices (XCI) for example, which will probably include a new version of Xen in a future release. Also Citrix XenServer which derives from XCP and Citrix XenClient which derives from XCI use Xen.