Disable screensaver

$ xset

...
To control Energy Star (DPMS) features:
-dpms Energy Star features off
+dpms Energy Star features on
dpms [standby [suspend [off]]]
force standby
force suspend
force off
force on
(also implicitly enables DPMS features)
a timeout value of zero disables the mode
...
For screen-saver control:
s [timeout [cycle]] s default s on
s blank s noblank s off
s expose s noexpose
s activate s reset
...

So, to turn off screensaver...
$ xset s 0 0
(The dmps also need to be disabled...)
($ xset dpms 0 0 0)