Wouldn't "high civilian activity" refer primarily to miners?

Probably. Barentsburg, west from Longyearbyen, is predominantly a Russian mining village. Svalbard is interesting in that it is part of Norway but citizens of some other countries are granted more rights than they’d have in the rest of Norway, and Norway also is not allowed to operate its military from Svalbard.

I believe it's basically all countries. There was a deal with other countries through the UN.

48. https://en.wikipedia.org/wiki/Svalbard_Treaty

In practice it's a visa-free zone. Anyone from anywhere can settle in Svalbard as long as they can get there. Of course, not many want to, so it's a bit academic.

There's was/is also Pyramiden to the north east, also a mining town but closed down in '98