A list of world shaders can be found in your Toribash folder -> data -> shader
Plus, there's a lot of downloadable world shaders in here.
Also, you need to have working Shaders to get those to work...
I don't know what that world shader is, though.
Same exact thing as a shader, means it covers the entire screen, the toribash 'world'. Mostly called environment shaders or something.
and as for something you 3 didn't answer, it doesn't cost anything, it's totally free.