where to get VOM licensing guide (if it's licensed)
VOM (Base) is free. You can download it from http://go.symantec.com/vom/ .
However, there are some advanced features of VOM that are paid. You can read about them and licensing for the same in the admin guides. These are available at the link above, but I am pasting the links below for convenience:
VOM (Base) Administrator's Guide (see chapter 15):
VOM (Advanced) Administrator's Guide (see chapter 5):