NeverWinter Nights 2 has been removed from the Mac App Store with no warning about 2 weeks ago. I only found this out today. Aspyr recommends that people that bought it, back it up (to a DVD-DL, external drive, etc). Initially, it was totally gone from the App Store (couldn't be redownloaded) but since April 5th, redownloading is once again possible for people who bought it. Aspyr hasn't said how long customers will be able to redownload the game. Also, Aspyr has yet to comment on why they would not warn customers in advance when a license to a game they sell is about to expire.
http://support.aspyr.com/entries/21233386-back-up-your-macapp-copy-of-neverwinter-nights-2
http://support.aspyr.com/entries/21233386-back-up-your-macapp-copy-of-neverwinter-nights-2