I don't think that's a valid comparison in this case. You aren't advertising another place to buy the same item, you are telling people how to buy content for the item they obtained from Apple's App Store that is (a) necessary for the item to work meaningfully and (b) is not sold through Apple's App Store. Are you completely confident that if Walmart, for some reason, sold video game consoles but didn't sell the actual games for the console, they would maintain an iron-clad prohibition against telling their own customers where those games are available?
