Source : Free On-Line Dictionary of Computing

free software
     
        According to {Richard Stallman} and the {Free Software
        Foundation}, free software is software that everyone is free
        to copy, redistribute and modify.  That implies it must be
        available as source code.  It does not imply that it is free
        of charge, so anyone can sell free software so long as they
        don't impose any new restrictions on its redistribution or
        use.
     
        {This dictionary} is free in this sense, though it is not
        really {software}.
     
        There are many other kinds of "free software" in the more
        obvious sense of "free of charge".  See "{-ware}".