If you hang it on your wall at home, you don't have to add anything to it. If you /redistribute/ it, then you have to give the license.
So... does that mean if you take a picture in your house with the GFDL picture in the background, its a derivative work and you have to glue a 1 pt font copy of the GFDL on the back of the 5x7s you are sending out in your Christmas cards? :)
Angela