Sam Jackson has been in a number of games, normally reprising a role he's played on-screen. He has never, to the best of my knowledge, been in a Heroes of Newerth movie. Or TV show, for that matter.
Still, the little MOBA-that-could has enlisted his services regardless, resulting in the announcer pack you see above.
If you don't feel like watching, yes, he says motherfucker. Repeatedly. I'm sure it was in the contract.