Let's make the core issue clear first. Lennart Poettering, creator of systemd, an init replacement daemon for Linux, is proposing systemd as an external dependency for GNOME-Shell in GNOME 3.2. Since systemd has Linux as a dependency and won't be ported to other operating systems (which would be a very difficult undertaking anyway due to its Linux-specific nature), it would effectively make GNOME a Linux-specific desktop environment.
Obviously, not everyone is happy with this idea. Debian, for instance, also has versions using the FreeBSD or HURD kernel, and on these versions, GNOME would no longer be able to run. Other than these niche versions of Debian, it would also sound the death knell for GNOME on Solaris and the BSDs.
Jon McCann, Red Hat hacker and the main driving force behind GNOME-Shell, takes the idea even further. "The future of GNOME is as a Linux based OS. It is harmful to pretend that you are writing the OS core to work on any number of different kernels, user space subsystem combinations, and core libraries," he states, "That said, there may be value in defining an application development platform or SDK that exposes higher level, more consistent, and coherent API. But that is a separate issue from how we write core GNOME components like the System Settings."
"It is free software and people are free to port GNOME to any other architecture or try to exchange kernels or whatever. But that is silly for us to worry about," he continues, "Kernels just aren't that interesting. Linux isn't an OS. Now it is our job to try to build one - finally. Let's do it. I think the time has come for GNOME to embrace Linux a bit more boldly."
Of course, and I can't stress this enough, it's a mere suggestion at this point, and by no means any official policy or whatever. The fact of the matter is this, however: if systemd becomes an external dependency for GNOME-Shell, this is effectively what is happening anyway. GNOME-Shell requires systemd which requires Linux. For all intents and purposes, it would turn GNOME into a Linux-only project.
Another important figure in the GNOME project, Dave Neary, isn't particularly enthusiastic about this idea. "This would be a major departure for the project, a big kick in the face for long-term partners like Oracle/Sun, and also for other free operating systems like BSD," he argues, "Are you sure you're not taking the GNOME OS idea a bit far here? Are we going to start depending on kernels carrying specific patch sets next? Or specifying which package management system we expect GNOME distributors to choose?"
The argument in favour of just focussing on Linux exclusively goes like this: why should GNOME be held back by advances in technology simply because Solaris and the BSDs can't keep up with the fast pace of development in the Linux kernel? I'm sure maintaining this kind of portability is a major pain the bum for the GNOME project, as it can, at times, hold them back in embracing the latest and greatest the Linux community has to offer.
All in all, I'm not really sure where I stand on this. I'm sure our readers will post some interesting insights which could help us undecided folk sway one way on the other.