It's like asking if NPR, The New York Times, The Washington Post and CNN are biased?
Actually, it isn't. All of those entities you cite present themselves as "objective" "news" organizations (except maybe NPR). And therein lies the problem. FreeRepublic is a discussion forum. The question of whether or not it is biased is meaningless.
Difference is, FR admits it is a conservative forum. They pretend objectivity.