It doesn't sound like you'll need to buy it.
In the article Herm posted, valve said, "...Insurgency Beta 3 will be powered by the Orange Box Engine by Valve. As long as your SDK - Base is updated, you will NOT need to buy the Orange Box."
If they're saying you don't need to buy the Orange Box to play Ins, you probably don't need to buy Ins, either; at least, that's what I take from that statement.
Oh I know beta is free, I think I misworded my post. I was asking if when beta is over if the actual game will cost money. If you remember way back when Steam was introduced Counter-Strike 1.6 Beta was free for months and months but than they were done with beta and they started to charge, I was just wondering if this was the same situation. But it doesn't matter, I would pay for this game.













