The RSS 2.0 specification is copyrighted by Harvard University and is frozen. No significant changes can be made (although the specification is under a Creative Commons licence) and it is intended that future work be done under a different name; Atom is one example of such work.
i had it completely wrong the whole time, i actually thought Atom was kind of a fork from the frozen RSS 2.0. That it had the same structure, just with more fields - to put it simply, RSS 2.0 with more features.