Our "home" number has been through nettalk.com
We want to 'port' that number for use on the OBi. Is this possible?
We don't want to use the Nettalk anymore, but we want to keep the number.
So that outgoing calls' caller ID shows up on receiving end as our Nettalk number.
You cannot generally port a "land line" number to Google Voice. There is a way to port that number to a mobile carrier and then port it as a mobile number to GV. It's a fairly involved process that you can find searching through the forum.
You should be able to port that number to a premium service, such as Anveo or Vestalink, and then use it on an Obi. I'm sure my comments will be followed up by others, but the answer is yes you can use that number with an OBi.
Here is a link to approved service providers https://www.obitalk.com/obinet/pg/services/spoptions