What are some alternatives?
When comparing GNUPGK and gpg4usb.org gpg4usb, you can also consider the following products
GPG Suite - Use GPG Suite to encrypt, decrypt, sign and verify files or messages.
GPGTools - Use GPG Suite to encrypt, decrypt, sign and verify files or messages.
GnuPG - GnuPG is a complete and free implementation of the OpenPGP standard as defined by RFC4880 (also known as PGP).
Kleopatra - Kleopatra is a certificate manager and GUI for GnuPG.
WinGPG - WinGPG – an open source encryption tool for Windows
PGP Tool - PGPTool allows you to encrypt and decrypt files. It's free and easy to use.