DS does use shaders - what the base version doesn't have is an equivalent of Poser's Material Room to turn a network of nodes into a shader on the fly. More to the point, DS doesn't even try to read anything but the basic (meaning Poser 4/PoserPro) material settings from a Poser file - it completely ignores the shader tree even when the default shader supports equivalent features (such as displacement). In order to get a comparable result from DS, if it's possible, you would have to adjust the specular settings, probably switch to the Skin lighting model, and perhaps apply maps for things like Specular strength and/or colour, if the character uses them. If the character uses things like procedural functions then that wouldn't be possible in the free DS, even with add on shaders, though is someone set them up in the DS Advanced Shader Mixer and saved a materials preset that would be usable in DS base.

To the best of my knowledge, Poser's Firefly is also based on a Renderman-compliant engine though it doesn't allow you to use hand coded shaders.