Hmm, I'd be interested in learning more; sounds like the kind of position I want. :-) Around here (Nordic region) I don't know of any such positions though. There are teaching-only positions, which can be a good option if you like teaching but not research: no grant or publication pressure, just a stable job with reasonable work hours. And there are regular faculty positions, with the usual teaching/service/research/management mix. But I don't know of an option to go research-only, at least in CS. In some areas you could work for a state agency as permanent research staff, but I don't know of any that do CS research (civil-service research positions do exist in areas like historical archives, social science, energy policy, international relations, healthcare policy, etc.).
edit: I did think of one place with such positions, the French state technical research institute INRIA. Maybe I should learn French...
My experience is that it's not necessary the case. Even when such jobs exist ("low-salary" permanent research positions that may exist in some european countries for instance), a lot of people still prefer to take a professor position at some point.
Also, passed a certain age, some researchers find themselves less productive research-wise and want to do other things.