In case you're not familiar with CDDA, here's some neat infos to know before considering to buy the game:

-Cataclysm: Dark Days Ahead is a free open-source game available at cataclysmdda DOT org/releases/

-This steam version has only two purposes:

1. To support the developer behind the steam version (KorGgenT).

2. Prevent a potential third-party from commercializing the game.

-The steam version will only contain the LAST stable branch of the game. NEW stable branches are usually released every 16 months, you can gain access to "experimental" unstable branches on the CDDA website.

-Nobody else in the development team benefits from the sales of the game. They have however approved of this release.