Dystopia, a total conversion of the Source Engine that requires Half-Life 2, could arrive on Linux, in the coming months.
Given the fact that Half-Life 2 hasn't been ported on Steam for Linux yet, and there's no telling when it will be launched by Valve, the fact that it showed up in the CDR databe as a Linux title is rather strange.
Dystopia is a multiplayer game at its core. It pits the Punk Mercenaries versus the Corporate Security Forces, in a cyberspace environment.
The information about the Linux version is taken from the CDR database and by no means is it completely certain. The CDR Database is a record of data that describes every Steam game and subscription provided by Valve for the Steam service.
Usually, the new entries in the Steam database are first visible in the CDR Database before their official launch.