MaryMaggotFace yes, but the warning was posted BEFORE they were able to react to Sawbones explaining that you shouldn't do that with freebies. It's not a well-known rule outside of people who regularly participate in freebies that freebies shouldn't be sold/traded off.
Even if there IS a large amount of characters labelled as "up for offers", all it means is that they were willing to let somebody else have the design if they so pleased. It doesn't mean that they claimed the design for free to only to make a direct profit, and it is not any of our business to assume that this is the case. More likely than not, it is just a mistake out of not knowing of about this rule yet.
There is no need to be suspicious unless this sort of behavior continues after an acknowledgement of the warning (which I'm willing to bet won't happen).