The Mowitz library is Free Software. All widgets are released
under GPL, LGPL or MIT/X style license. The reason for the multiple
licenses is that the code was written by different people and the
original licenses differ.

What this means is that if your application will be released under
the GPL, like most free software these days, you won't have a problem.
If you are planning on developing a commercial application and
distribute binaries without source, you'll have to remove any
code in this library which is under the GPL (because the GPL would
otherwise force the completed application under the GPL as well).
See source code for details.