commercial print use of OSM on greeting cards

Hello there,

I have an idea for using your maps as a background for printed greeting cards - using the "Download" button on your maps to obtain a .png image of your map.

I believe, from the copyright page that this is acceptable use of OSM. Am I correct?

If so, how do I appropriately credit OSM in print? Would the following suffice (printed on the card):

"MAP image IS COPYRIGHT © OpenStreetmap.org used under licence at www.creativecommons.org/licenses/by-sa/2.0/"

Many Thanks for your advice,

Glen