Every side in an RFTS scenario can have its own, unique R&D tree. Since sides in an RFTS scenario aren't restricted by licences or story lines, there are effectively an infinite number of sides, which means that R&D can never become stale or predictable.

This screen shows an Attack Cruiser hull being researched. The next items to be researched are in the queue, with other available techs shown on the R&D ring.