how do you do a onRender scriptlink

I have this script http://members.iinet.net.au/~cpbarton/ideasman/render_fake_arealamp.py
and it needs an onRender scriptlink but I havs no clue what that is

Load your script in the Text Editor. In the Buttons window goto Panels, Script. Click New and add your script. Then in the menu choose Render.

%<

Cool! weird though the script makes the lights extra but they do not become a sphere dome effect at all just stacks of lights