Soundmodem was downloaded from 
http://www.baycom.org/~tom/ham/soundmodem/

It is Copyright (C) 1999-2001 by Thomas Sailer (sailer@ife.ee.ethz.ch)
and released under the GPL license.

On Debian GNU/Linux systems, the complete text of the GNU General
Public License can be found in `/usr/share/common-licenses/GPL'.