Personally I am particular to MBS add-ons and think it was well worth the money. They take a bit of getting used to and have a learning curve, but they are, in many ways, more effective than the stock Xojo abilities.
If I were doing this, I would use the MBS package, but that is just what I would do…
Anyway, the issue is a different one. I had understood that the line would not compile or work but it does. The comment has been added by the Xojo employee who created this example application. So the OP was about why this comment exists.
The example doesn’t use a AddressbookData, and I think it should. I tested this to make it possible to exchange addresses between our own system and the Mac addressbook. I think it should be:
Dim address As New AddressBookAddress
Dim Indata As AddressBookData
contact.Addresses.Append(AddressBookData.LabelWork, address) //add an (empty) address
Indata=contact.Addresses
address=Indata.Value(0)
address.StreetAddress = "PO Box 162181"
address.City = "Austin"
address.State = "TX"
address.Zip = "78716"
contact.Addresses.Append(AddressBookData.LabelWork, address)