When you are running Xfree86 as root, xscreensaver does not work
for several reasons.  First, it sets its uid/gid to nobody and then
it can't access the screen; adding a xhost +nobody would be a very
bad idea.  It also has problems with the .xscreensaver file (according
to xscreensaver-demo) because it will read ~nobody/.xscreensaver but
xscreensaver-demo will modify ~root/.xscreensaver.

I don't normally run X as root but was doing so while initially
setting up a system.  Also, some of the redhat system management
tools are designed to be run as root.

Also, when xscreensaver is run as an ordinary user, it does not
lock the linux virtual console switching which makes it completely useless
as a screen locker.