Veritas have changed the licencing for VMware fairly recently.  Check it 
applies to your version....

Basically if you backup the ESX server you need a redHat client licence as 
per the actual hardware.

Then you need (assuming you are using...) one client licence per OS type 
you run as VMs on that ESX server (*does not apply to IBM mainframe class 
*).

So if you have say a HP proliant...with 8 Windows VMs and Two Linux VMs...

One RedHat client for the ESX server
One Windows client
One Linux client

Cheap...

But BWR if you run parallel backups of several VMs on one physical server, 
don't expect good throughput.

William D L Brown