This is a simple displacement shader. If disp_enable is 0, then you'll get a bump. There's also an option to add a second map as bump (you can get some extra detail using a bump over a displacement map).

There's also a couple of variables that export undisplaced P, that can be used by some shaders to avoid errors when "trace displacements" is not enabled in the geo attributes.

This shader has some attributes not used in the code, so you can simply remove them. But I think they'll get used in future versions of 3delight (by looking at the changelog)..

Anyway, hope it can help you creating something more :)