The Cuusoo releases generally aren't available through the Lego stores (or any other retail outlet that I am aware of really).
You pretty much have to follow the site for purchase information and mark your calendar for the date and time.
I haven't actually purchased any set yet, so I can't speak to the ease or difficulty of acquiring a set, but, depending on the price point, I'll definitely be wanting this one.
I do wonder though, is Lego doing the legal work to acquire licensing rights for these, or is there some loophole that lets them bypass that since these are "fan designed" and limited release items?
I could have sworn I saw the Minecraft one at my local Lego store..... although I could be wrong.