Well, putting sarcasm aside, I think I understand your question.
OBi110 has only one port for the phone. Therefore, you will use your line 1 of the phone to make and receive calls on both GV and PSTN lines. If it's a desk phone where one person is talking anyway, then it doesn't matter - you will be able to switch between GV and PSTN calls in better ways than 2-line phone allows you. However, if you have additional handsets, 2-line phone allows two people have simultaneous conversations. OBi110 does not allow it.
In summary, you can use GV and POTS, but you cannot use Line 2 of the phone with OBi110.
Hope that answers your question - and yes, it was also asked and answered many times before.