Customers can buy the Red Hat Enterprise Linux with Smart Virtualization which includes both RHEV and unlimited RHEL guests for use as the guest operating System. http://red.ht/1Tzr9pq
RHEV stand alone subscriptions include the RHEV-H hypervisor and RHEV-Manager, they do not include the rights to use RHEL as the guest operating system in the virtual machines being managed by RHEV.
The customer would purchase this separately by buying a RHEL for Virtual Datacenter subscription.
Please note that RHEL hosts generate additional subscription costs that are not included with RHEV (see https://www.redhat.com/apps/store/server/ for details). RHEL hosts are priced by sockets (2, 4), number of virtual guests included (1, 4, unlimited) and subscription levels (Standard/Premium).