Hi,
NetBackup for VMware is more an umbrella name. It is the integration with VCB/vStorage (depending on VMware/NetBackup versions). It includes features like VM's auto discovery, off-host backup (done on VCB proxy in fact), granular restore ...
In your case (VI3), you need to install VCB on a Windows host. Regarding licensing (as of NBU 6.5, changed in NBU 7.0), you need to license 1x Enterprise Client per guest OS type and 1x database / application pack per database and/or application type per VMWare host.
For instance, let's assume that you have 2 ESX hosts as follows:
ESX1: 10 windows VM's, 5 Linux VM's, Oracle, Exchange, SQL Server
---> 2x Enterprise Client (Windows + Linux), 3x database pack (Oracle, Exchange, SQL Server)
ESX2: 5 windows VM's, SQL Server
---> 1x Enterprise Client (Windows), 1x database pack (SQL Server)
Note: Database/application pack does not include SAP agent which is licensed apart.
All that changed with NBU 7.0. It is now 1x Enterprise Client per ESX host + 1x database/application pack (if any database / application running within VM) no matter how many different guest OS or database / application you have running within VM's.
Regards, Olivier.