As the title says I cant seem to find any information about this , it does have a notice saying it requires 3rd party software but it doesn't say what.
The other reason I ask is because MW2 always required steam and there was no alternative and I dont want to buy it from steam again.
Best Answer
It does require Steam. The game doesn't run without it, even the retail version requires Steam.
How do I know? I bought it from Direct2Drive.
You can even enter the serial number you get from D2D into Steam ("Add A Game...") to get around the D2D download manager.