I personally don't think so as doing that excludes Free Software like BSD etc that are not part of GNU/Linux. There are free software for M$ Windows too. The goal should be to spread Free Software and not only GNU/Linux. Naming GLUG and supporting Free Software can give newbies an idea that GNU/Linux as the only Free Software and that is unethical as it doesn't respect the other Free Projects. There are lots of people working hard to attain freedom outside the GNU Project. I personally know a group that is trying to create a Free Software package that works on M$ Windows. It will be unfair to projects like these (I think so) if FSF (which was formed to propagate the message of Freedom) supports GLUG and not FSUG.
GNU/Linux and GNU/Hurd are the priority for FSF as far as I understand. It is not that we are against other free OSs like FreeBSD. But those projects are not freedom protected and reason for their existence is not Freedom in computing. So I think our energy is better spend in strengtheing GNU based OSs.
Regards, Arun. -- PS: I personally make it a point to let people know that there are other Free OSs available.