The wxHaskell libraries are distributed under the wxWindows library license. The documentation is subject to the wxWindows documentation license.
See http://www.wxwidgets.org/newlicen.htm for the legal description of the license.
The wxWindows library licence is essentially the L-GPL (Library General Public Licence), with an exception stating that derived works in binary form may be distributed on the user's own terms. This means that it is possible to create commercial software with this library without paying royalties or disclosing source code. This is a solution that satisfies those who wish to produce GPL'ed software using wxHaskell, and also those producing proprietary software.
This library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the wxWindows library license for more details.