Customers can buy the Red Hat Enterprise Linux with Smart Virtualization which includes both RHV and unlimited RHEL guests for use as the guest operating System. http://red.ht/1Tzr9pq
RHV stand alone subscriptions include the RHV-H hypervisor and RHV-Manager, they do not include the rights to use RHEL as the guest operating system in the virtual machines being managed by RHV.
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 RHV (see https://www.redhat.com/apps/store/server/ for details). RHEL hosts are priced by socket pairs (can be stacked to the number of sockets in the server) and subscription levels (Standard/Premium) and are allowed to run up to 4 virtual guests in case they are not managed by RHV.