How much content overlap is there? (Quite a lot, power user could actually have OS specific categories) Do the respective communities agree with that? (One would need to ask on their Metas) Does the software support that operation? (Merging of two sites, adding tags, selecting a new design set, how to merge site specific settings?) How could we measure the success of such a merger? (Questions or answers or views per time?)

Re "does the software support it?": I think we can assume that if this is what both communities want, we can find a way to do it. (Probably through direct database manipulation by one of the devs with access.)

Monica Cellio‭ Or it could become even a full-flegded feature over time. Not only mergers but also splits are imaginable. It sounds not trivial though. What about user privileges, or links in the edit history or for search engines a rewrite of old URLs (people might have linked from outside to questions or answers on these sites). The technical requirements for such an operation could probably be discussed separately.

Trilarion‭ agreed -- not trivial, but when we set up Software Dev we did so anticipating that sub-communities might eventually split off, so nothing prevents it AFAIK other than deciding about things like the points you raised. Merger is probably the easier case: nobody's going to lose abilities, and URL redirects can be kept in place. If the two communities decide they want to merge (which should be discussed on both of their metas), then we can work out the technical plan for how to do it.