Yes.

And your main adapter has two lines already if that's all you need.
On the main ATA you can have two simultaneous calls going.

The key difference is the BYOD, or soft phone does not allow international calling, and uses different credentials from the plug&play VOIPo ATA.

VOIPo doe not provide personnel to support BYOD, but there is a user forum here: http://forums.voipo.com/forumdisplay.php?f=28