If you mean the gpg command line program, that comes pre-installed with the N900 (gnupg package) and runs fine.

Unfortunately, the package claws-mail-pgp-plugins to integrate gpg into claws mail has some broken optification links: The symbolic links to the binaries (.so-files) replace the files during installation and point to themselves. I manually extracted pgpcore.so, pgpinline.so, and pgpmime.so and installed them into the appropriate dirs. Now GPG works fine in Claws-mail.

Unfortunately, there is no bugtracker link for this package to report this ...