Well, Sailfish OS does use a lot of components that were originally developed or selected at MeeGo, like Ofono, Maliit, MIC, RPM, systemd, Qt based UI. Harmattan wasn't really that much MeeGo based - it had some components from it but IMHO it was closer to a final generation of Maemo - for example it still used deb packages and upstart. And for sure there was a substantial amount of system components and default applications that were and remained proprietary.