GM is term that predate MMORPG's It's referring to the person who runs a game of dungeons and dragons and control's the story. Gmod is just another way of saying Game Mod with "Mod" being a shortened form of the word Moderator. This is all common gaming vernacular. A lot of Wow's system where in add ones that 90%+ people used. But they did exist because I used them myself. A program with a download count of tens of millions upon tens of millions.

Not one person is blockong anyone from anything
Even with out oing into detail on the OP's views on the subject expressed in all her views. You do know the title is "Block first timers from the partyfinder" You're clearly the one who is a little lost on the nature of her idea.