Things You'll Need
Instructions
Have the person who already has the maps pack download go to your PS3. They need to login to their account from your PS3. Once they have loaded their account, they can access the PlayStation Network and all of their preferences; the purchase history will be available.
Once the new account has been loaded onto the second PS3, go into the store and find the DLC map pack for "Modern Warfare 2." Download the map pack to the second PS3. Because it's already been purchased, it won't require you to pay a second time.
When finished with the download, you will now be able to use the map packs on your PS3. However, the map packs only save to that particular PSN account, so it must be used to play with the downloaded maps in either the online or offline mode.