The material format in MH was primarily intended for configuring the shading within MH itself. But since it follows the general lighting equasion very closely, it should map to various renderers' material settings pretty easily.
There is definitely a difference between normal mapping and bump mapping, and while bumpmapping has mostly been surpassed by normal mapping, it has its uses in distinct situations. More generally, bump mapping is better suited for very small surface details like pores, as it responds better to mip mapping or aliasing effects, is reusable on multiple geometries (as it is not geometry dependent) and can also more easily be used as a tiled repeating pattern for closeup details.
You can read here for a more detailed explanation:
http://blog.digitaltutors.com/bump-norm ... ment-maps/bumpTextures are greyscale images, normalmap textures are the ones that usually look purple-ish.
Shaders in MakeHuman have not been finished yet, and the uber shader that incorporates all the material settings in MH is still on the roadmap. One day this will simply work. But if you select the right type of shader in MH, most of the effects will already work in some way.
As for how MakeClothes exports material properties: it's possible there are bugs in there, if you find them please report them. I have not tested these myself. I guess best is to check the mhmat file that MakeClothes produced, and see if that makes sense.