License

APBS is covered under the GNU Public license (GPL), which basically means you can copy it, change it, use subsets of it, redistribute it, etc.; however, you need to give credit to the original source and the original portion of the code must remain under the GPL.

Here is the specific licensing information:

APBS -- Adaptive Poisson-Boltzmann Solver
Nathan A. Baker (baker@biochem.wustl.edu)
Dept. of Biochemistry and Molecular Biophysics
Center for Computational Biology
Washington University in St. Louis

Additional contributing authors listed in the Contributing Authors chapter.

Copyright (c) 2002-2005. Washington University in St. Louis.  All Rights Reserved.
Portions Copyright (c) 1999-2002. The Regents of the University of California.
Portions Copyright (c) 1995. Michael Holst.

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.

This program 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 GNU General Public License for more details.

You should have received a copy of the GNU General Public License along with this program; if not, write to the Free Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.