The GNU Privacy Guard
Version 1.0.0 has been released on September 7th, 1999. The current stable version is 1.2.4.
GnuPG is Free Software. It can be freely used, modified and distributed under the terms of the GNU General Public License.
PGP, on which OpenPGP is based, was originally developed by Philip Zimmermann in the early 1990s.
for full details see http://www.gnupg.org/