A few days ago I mused on systemd and GNOME OS, yet it seems clarity is still required on the subject.
This is about the interfaces GNOME will require. While systemd is Linux only for technical reasons, the interfaces it implements can be provided by any replacement if so desired or needed. In many ways depending on the interfaces systemd provides is like the expectation GNOME makes of a platforms libc implementation. Systemd offers a promise to keep it’s interfaces stable, so anyone implementing replacements will not have to chase systemd.
So GNOME is not becoming Linux only, just setting some expectations for what the OS should be able to do in order to provide the best possible GNOME experience.
Naturally this will start with things the user cannot see. For example, replacing something like ConsoleKit – ‘a system-wide service that tracks [users] and sessions’ - won’t be that apparent on the surface but will serve to make the foundations of GNOME more reliable. In the long term this will lead to the implementation of stuff that will make you go “Ooh”.
For now, those concerned should simmer down and read the systemd proposal thread from May 20th, starting with Lennarts reply.