GNU Crypto is licensed under the terms of the GNU General Public License, with the "library exception" which permits its use as a library in conjunction with non-Free software:
As a special exception, the copyright holders of this library give you permission to link this library with independent modules to produce an executable, regardless of the license terms of these independent modules, and to copy and distribute the resulting executable under terms of your choice, provided that you also meet, for each linked independent module, the terms and conditions of the license of that module. An independent module is a module which is not derived from or based on this library. If you modify this library, you may extend this exception to your version of the library, but you are not obligated to do so. If you do not wish to do so, delete this exception statement from your version.
The effect of that license is similar to using the LGPL, except that static linking is permitted. GPL with that exception is sometimes called the Guile License, because the Guile implementation of Scheme (for embedding) uses this license.
You can download the latest software from ftp.gnupg.org/gcrypt/gnu-crypto. You'll probably want to use one of the FTP mirror sites, although the mirrors may not be current (most are synchronised daily).
Up-to-date source code for this project is available in the gnu-crypto module through CVS.
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