BTW, xVM Server has been folded into xVM Ops Centre:

"With all the interest in Eco/Green computing we expect a lot of buzz around this. However, the most interesting item is the release of a set of comprehensive x64 hypervisor management functions. Ops Center can now:

* Provision the xVM Server hypervisor onto bare metal servers. It can do these completely "hands off" and it can do this for multiple servers simultaneously. It does all required network setup and plumbing as well (a major hurdle for our EA customers)

* Creation of VM guests and provisioning of images to those guests (either via ISO install or network install)

* Guest snapshotting and backup

* VMDK file format support and import of VMware Virtual Appliances

* NFS and CIFS network storage support for guest and ISO images

* Live migration of guests from one host to another

* Virtual Pool constructs for policy automation across hypervisor hosts based on load, as well as automatic failure recovery

Ops Center 2.1 includes a bundled xVM Server beta that is available to all Ops Center customers, and we will be running a formal beta program with key, interested customers to ensure this works reliably and at scale for real enterprise deployments. If you are of of the existing hundreds of xVM Ops Center 1.0, 1.1, 2.0 or Sun Connection customer then you're eligible to upgrade to Ops Center 2.1 (which includes the xVM Server beta) for free. "

And, the guts of xVM Server is in OpenSolaris:

http://opensolaris.org/os/community/xen/docs/

http://blogs.sun.com/ptelles/entry/sun_xvm_hypervisor_part_i

http://blogs.sun.com/ptelles/entry/sun_xvm_hypervisor_part_ii

Again, this would have actually required a little research on your part. The sources aren't exactly obscure, either.