Sorry if I appear negative but I have strong feelings on this subject. As Felix poiinted out it goes against the spirit of freeware. It seems that as soon as you find something worthwhile in this world someone inevitably comes along & tries making a profit out of it. There will always be people willing to pay for things they're either too lazy or incapable of doing for themselves. Otherwise there would be no market for it.
I won't ask you to answer this but I have to wonder how much you think would be a fair price to repaint the average freeware aircraft.