PortableApps has an installer for GNUPG in the works that downloads gnupg for windows then installs it to a "CommonFiles" directory for all the programs to share. This NSS code/method could be adopted by Appupdater to install gnupg to a subdirectory of \Apupdater and then relatively link to it for use, rather than search the computer/user's $PATH. This would alleviate the issue with adding the path to the gnupg executable to the computer/user's $PATH
NSS Source code included in the installer to use as a reference. The common PortableApps Installer file will need to be installed also to have all the NSS code you need to implement a similar function in Appupdater.
GunPG installer: http://portableapps.com/node/11402
PortableApps Installer: http://portableapps.com/news/2009-06-30_-_portableapps.com_installer_0.91.7