Recently, Enkord has made all of the games, including Aerial Mahjong, free to play because they are focusing on two online games: Totem Tribe Jotun and Gunrox.
You can create your Enkord account and start playing/downloading the games now.
Aside from the mediocre gameplay, I love the music, and I love the SandS. I love all the soundtracks they composed. Still, I don't recommend this game at all.