PGP stands for Pretty Good Privacy, and GPG stands for Gnu Privacy Guard. PGP was written as copyrighted freeware under the Gnu Public License, and PGP was upgraded by turning it into a property program.
The upgrade was made because of legal defense costs and royalty issues associated with the export laws of the United States. PGP Corporation retains the new PGP program, and it is said to be more refined; however, GPG is an upgrade of PGP. GPG does not utilize the IDEA encryption algorithm. Windows frontends are also accessible for GPG other than the command line. The freeware edition of the PGP software package can be downloaded from the home page of PGP International. It is strictly for personal use and is not for commercial purposes. However, you may purchase it from PGP Corporation.