Stock N9 doesn't even run Meego (proper). It runs Harmattan, a transitional system which is more Maemo than Meego underneath. Nokia planned to evolve it into Meego proper, but never did since it soon sunk into the oblivion of WP. Some parts of Meego (not Harmattan) were forked by the community as Mer, and some other parts (namely Meego Handset) as Nemo. Sailfish is built on Mer and parts of Nemo, adding its own UI on top. All this (including historic evolution of Moblin and Maemo to Meego) can be pretty confusing for those who didn't follow these developments. See also this chart: https://github.com/kumadasu/tizen-history