The screensaver module in OS X has a command-line option that allows it to be run in the
background of your screen, as a replacement for the desktop picture. I found this in the
application bgscreensaver, which
contains an AppleScript to launch the screensaver module in the background, using a shell
command found by Michael Coyle at ResExcellence.
While this is pretty cool in and of itself, I wanted something that would let me run one
screensaver as the background, and have another one for my actual screensaver.