I believe that Death House is probably not AL legal until March 4th. Don't quote me on that, but it's what I've surmised because the instructions say that the season starts then. Since it's part of CoS, the safe bet is to wait until the official start of the season, unless the Admins declare otherwise.
Anything published by WotC is legal when it is released. (Per AL Admin). Robert Adducci confirmed this module is currently playable. SO you can start now if you want. (We are starting tomorrow night).