GameSpot reports after an interview with DICE the unlockable weapons in Bad Company are free now:

"I should pretty much start at the end, we listen a lot to what people say out there. I think that's important to show, because we don't have time to comment on everything, because there's so much noise out there, but DICE is built upon the multiplayer community, and we do listen to what people say out there. When we saw this big uprise about people that really felt it was dissatisfying that some people bought the Gold Edition, those five weapons you couldn't get or that you had to buy if you had the ordinary version of the game, that we just decided that all weapons will be free in the game, and that's how it is now."

"These Gold Edition weapons, we won't give away, you have to do something as a gamer. The Gold Edition guys and girls that actually buy that game will have some time where the weapons are exclusive, because if you don't buy the Gold Edition, you have to earn them. That means you have to rank up all the way to the top rank, which is rank 25, and then you have a massive unlock of five new weapons which are the same that are in the Gold Edition."