Having a garage sale one time is not running a business because running a business requires an ongoing operation.  If you had garage sales regularly on a continuing basis, it is possible that it may be construed as running a business, but a one time garage sale is NOT running a business.Unless there is some prohibition in the CC&Rs (conditions, covenants and restrictions) prohibiting a garage sale or requiring the prior consent of the HOA, the fine is unwarranted and should be challenged.