The license of SCM (like Guile) consists of the GNU GPL plus a special statement giving blanket permission to link with non-free software. This is the license statement as found in any individual file that it applies to:
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, 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 software; see the file COPYING. If not, write to the Free Software Foundation, 59 Temple Place, Suite 330, Boston, MA 02111, USA.
As a special exception, the Free Software Foundation gives permission for additional uses of the text contained in its release of SCM.
The exception is that, if you link the SCM library with other files to produce an executable, this does not by itself cause the resulting executable to be covered by the GNU General Public License. Your use of that executable is in no way restricted on account of linking the SCM library code into it.
This exception does not however invalidate any other reasons why the executable file might be covered by the GNU General Public License.
This exception applies only to the code released by the Free Software Foundation under the name SCM. If you copy code from other Free Software Foundation releases into a copy of SCM, as the General Public License permits, the exception does not apply to the code that you add in this way. To avoid misleading anyone as to the status of such modified files, you must delete this exception notice from them.
If you write modifications of your own for SCM, it is your choice whether to permit this exception to apply to your modifications. If you do not wish that, delete this exception notice.