This FAQ answer is the most moronic thing I have ever heard.

When you want to watch a movie, fire up xscreensaver-demo and select Mode: Disable Screen Saver from the option menu, which means not to blank the screen at all. When you're done watching the movie, re-select your previous mode.

That's kind of lame, I know. You should ask the author of the DVD-playing software you are using to add explicit support for xscreensaver to their program.

So let's get this straight, you want everyone who might write a program that shouldn't be interrupted by the stupid screensaver to implement xscreensaver-specific logic to keep the screensaver from coming on, and you don't want to give us end users an easy way to turn it on or off in a script. IDIOT!!

Oh it gets better. He then goes on to explain how developers should "add explicit support for xscreensaver". They should set up another thread to periodically make a system call, e.g.:

if (playing && !paused) {
    system ("xscreensaver-command -deactivate >&- 2>&- &");
}

I'm utterly amazed at the idiocy. But let it not be said that I rant without action:

#!/bin/sh
(
while true; do
    sleep 60
    xscreensaver-command -deactivate &>/dev/null
done
)&
trap "echo 'Reenabling XScreensaver (IDIOT!!)'; kill $!" 0

xmess nes -cart ~/games/mario.nes

If you're ambitious, you could write a generic wrapper program inspired by sudo or openvt.