It seems on reading the GPL FAQ and in particular http://www.gnu.org/licenses/gpl-faq.html#GPLIncompatibleLibs, that: The GPL normally extends itself to all of the program * including all library dependencies *, I'll leave aside the issue of whether this is legal, and instead point out the section which reads: "If you want your program to link against a library not covered by that exception, you need to add your own exception, wholly outside of the GPL. This copyright notice and license notice give permission to link with the program FOO: Copyright (C) yyyy <name of copyright holder> 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 In addition, as a special exception, <name of copyright holder> gives permission to link the code of this program with the FOO library (or with modified versions of FOO that use the same license as FOO), and distribute linked combinations including the two. You must obey the GNU General Public License in all respects for all of the code used other than FOO. If you modify this file, you may extend this exception to your version of the file, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version. Only the copyright holders for the program can legally authorize this exception. If you wrote the whole program yourself, then assuming your employer or school does not claim the copyright, you are the copyright holder--so you can authorize the exception. But if you want to use parts of other GPL-covered programs by other authors in your code, you cannot authorize the exception for them. You have to get the approval of the copyright holders of those programs. " The last paragraph is particularly odious it seems to me, especially if you are trying to combine Boost with GPL'ed libraries into one GPL whole. One final point, I note that some libraries under non-GPL licences contain explicit exceptions along the lines of: "4. If PCRE is embedded in any software that is released under the GNU General Purpose Licence (GPL), or Lesser General Purpose Licence (LGPL), then the terms of that licence shall supersede any condition above with which it is incompatible." But having said that, the new Boost License seems to be most like the licenses that the GPL folks consider to be "compatible", so maybe we just need to hasten the provision of the new License to all of Boost. John.