No Killkroozers involved, chromedog. Full-on space hulk.
Also, the world was dead, suspiciously so, and was being investigated by the Imperium.
Eventually the Necrons do wake up and kill everyone but it's thousands of years after the setting of Gorkamorka.
The official races for it are:
-Orks
-Rebel grots
-Muties (mutant cowboys)
-Diggas (human savages)
There's several more added by fans too.
Perhaps other people only play Orks vs. Orks but I've seen a lot of variety in my campaign.
If you're interested in the game the rulebook and sourcebook are available for free from
GW:
http://www.games-workshop.com/gws/content/article.jsp?community=&catId=cat410008&categoryId=1100014&aId=5300012
There's an expansion pack called "Digganob" that adds the three other races but that you'll have to find for yourself.