Artha is a free cross-platform English thesaurus that works completely
off-line and is based on WordNet. Stable releases for download are
currently available for GNU/Linux and Microsoft Windows; it is tested
on major Desktop Environments like GNOME, KDE, Xfce, etc and on Microsoft
Windows XP, Vista and 7. Artha is released under the GNU General Public
Licence version 2; hence you are free to copy/redistribute it.

WWW: http://artha.sourceforge.net/wiki/index.php/Home