Hayabusa...like the ninja,
   Not sure if anyone got back to you on this issue, but this is the way the IP-on-the-Fly license works:
     Install license, change Network Protocol to IPotF under System Config.
     Reboot NBX
     After the system comes back online, there will now be a radio button for IP Addresses under System Config.  This field is used for a pool of addresses you specify that are used for IP calls.  When a call that requires IP is initiated, the NBX will grab an address from that pool to be used for that call only.  Once the call is complete, the address is returned to the pool.  
     If you are setting up your IP phones, they must first be discovered locally.  I believe it's Device Config. to change the IP Settings of the actual phone.  Once this is completed, you can then move the phone to desired location.  
     No additional software is required, although there may be limitations or improvements, depending on the software your are running on the NBX.
     As far as the price difference, I have no idea why there would be such a broad price range on this license.  The keycode is only for IP-on-the-Fly, I believe, and doesn't contain any additional features, such as VTL.
     Hope this helps!!