Is Nonfat Dry Milk Skim?

Yes, it is. Here in Canada, they call non-fat dry milk skim milk powder, but its the same thing.

Is milk powder the same as real milk?

Editor's Note: Milk powder is dried milk, so it is made from real milk but has all of the water (and quite often fat) removed. If you mix it with water, you will get something like skim milk.