DLC should be part of the game, this is not. It is a link to an external paid site, and it doesn't even work on top of that. I followed the link and the "premium" content was not unlocked after buying this and they wanted to charge me more to get the content I already paid for with this. Thankfully GOG refunded this purchase. Make this an offline, stand alone map with no DRM, and I will think about buying it.
