This does not strictly fall under the Advertising Restriction. The poster is not advertising their product, just announcing a product that might be helpful to players of the game. It is much the same when someone posts that Amazon has a sale on a game or something like that.
This thread is OK and it is nice that there is an App for This.
Plus, there are
free ones at the iTunes store as well - so yeah.

From playing WoW (very short time) I figured there were apps for this game too and checked a few weeks ago. Most looked pretty sweet, but a fully populated map was too spoiler-ish for me.

I prefer to just check a wiki for specific locations on an as needed basis.