Khorne isn't an official roster, it's something that was unique to Cyanide's BB1 game. That said, the XML files did reference khorne as well as an unspecified slaanesh team. BB1 had a "legendary edition" just as BB2 did, followed by a "Chaos Edition" that introduced the khorne team. We may be looking at a third "expansion" in late 2018 or some such.
Following the vote held in September 2017, the NAF Committee has decided that Bretonnians and Khorne will be added as races to the NAF database.