Society finches are called "society" for a reason: they are a domesticated finch, and are good-natured and even-tempered. They're also good parents, and are often used as "foster" parents for other finches, since they'll help raise just about any bird. Several years ago when one of my Zebra finches was shunned by the other Zebras in the Finsterium, the Society Finsters took her right in. I keep hoping they'll do the same with Frank. And, it looks like Frank may be hoping for that, too.
This photo shows Frank sitting on the porch of the nest box that the Societies sleep in. There are a few Societies inside — although you'll have to take my word for that. Frank was sitting there so long some of the other birds seemed a bit irritated — the Finsters inside wanted to get out, and the ones outside wanted to get in.
Maybe one day Frank will start sleeping inside with them.