Hello,
well, there's a couple of things going on. What version of DBC are you using? 1.20 has some material settings that influence how light behaves.
Shadows are never "cast" per se in DBC. Even if you have an object that should be blocking the light source. In the matrix example you reference, I believe there is a light object created that can be referred to as a dark light. That's a light where the color values are set to negative rgb(-255,-255,-255). What this does is instead of casting light as the color, it absorbs light of the color. The dark light is what you are seeing in the example.
Now, as far as the cube... to make more convincing lighting effects, it's up to the normals of an object. A normal is calculated per polygon and then per vertex. That means, the more polygons, the better the lighting will look. A DBC cube only has 2 polygons per side so the lighting is pretty limited as opposed to a matrix which has many polygons so the subtleties of the lighting are more promounced.
Here's a rewrite of your example. I did it in DBC 1.20. It runs a little darker in 1.13. I've attached a cube that comes in the example files in case you don't have it. It has many polygons.
set ambient light 0
color ambient light 0
make light 1
color light 1,-255,-255,-255
`set point light 1,0,10,0
set spot light 1,5,20
position light 1,20,50,0
`set point light 0,0,50,0
autocam off
position camera 0,20,-30
point camera 0,0,0
load object "gridcube.x",1
scale object 1,1500,1500,1500
position object 1,0,-25,0
point light 1,5,0,0
make object sphere 2,10
position object 2,0,10,0
wait key
Enjoy your day.
