Unfortunately there is no way to produce REAL light with a script (see
here), the aim, or at least my aim, being to use as few add-ons as possible.
What I've been trying to do is to create a flare (which IS a source of light), and then a loop to setpos continually where you want, but it takes about two seconds for the flare to ignite, during which it keeps falling to the ground :-\. That means that you can't stick it on a house ceiling or other.
I give you the script anyway, so you might figure out what you can do with it (it's quite plain, really) :
_object=_this select 0
_height=_this select 1
_flare="fire" camcreate [getpos _obj select 0,getpos _obj select 1,_h]
#loop
_flare setpos [getpos _obj select 0,getpos _obj select 1,_h]
~0.001
goto "loop"