How can you play kino der toten for the PC for free

You don't Kino der Toten is a Map for Call of Duty Black Ops that comes with the game. Call of Duty Black Ops for the PC is not free and Kino der Toten works only as part of the Call of Duty game. Just buy the game that is why it is the best selling game in the USA ever. If they could just play it free why would they have all the sales on the game