Do you need an additional license key to enable the SFP port if your application only requires Fiber?
(Out of the box, the PTP 820 comes with a GigE port. Is this limited to Copper, or do I have to buy another activation key to enable ETH2, which is an SFP port?)
ANSWER: No, if you're only using one GigE port, you don't need any additional GigE activation key or license.
If I want to use the PTP-820S POE/Copper port for Out of Band Management, and I want to use the SFP port for data, what is the part number for the license key that I need to order?
If we would like to use optics port for data, we don't need additinal license? MGMT would be over MGMT Ethernet port. So we would use only one port (fiber optics) for data and another for MGMT. If we use data port for in-band MGMT, it doesn't change anything, correct?
That is correct. It doesn't matter which port you use (ETH1, ETH2, or ETH3 (PTP 820S only)), or how you use it. If you only use one Ethernet port, you won't need an additional port license.