If MW3 is anything like MW2, getting it to work on a LAN is possible but there's a hell of a lot of fucking around involved. Of course cracked games are not endorsed or supported by Respawn (though there's plenty of reason to feel, if you're a legitimate owner of a game, that you should be able to play it at LANs).
The dedicated server itself looks like the same one that goes way back to cod1/q3 and most of the commands are the same.. they just added steam based authentication so in theory it should work fine