Most people use DM instead of GM or another specific game term to refer to the person running the game. Mostly because this is a comic based on a DND game and most of our other long discussed gaming comics are DND based.
Then of course comes the inevitable euphemisms. Mainly because of the fact that GITP forums are supposed to somehow be more kid friendly than every single other thing on the site, and most of the prominent posters who were ever that young to begin with have long since become adults.