This is the package signature as generated by The GnuPG. This signature identifies the party that created the package. By verifying it you are sure that the package coming from a trustworty person or organization.
Here is the package signature:
-----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.4 (GNU/Linux) iD8DBQBEyxffqesEzEdeXBERAh56AJ4oCIxTU9IVmbgvB6j7R2cZPV09CgCfT8VG HCV2VOTvnL1jcNtNBa8psBI= =tR4A -----END PGP SIGNATURE-----
You can save this signature in a text file (e.g. mozilla-thunderbird-1.5.0.5bg-i686-1gds.tgz.asc) in the same directory where the package file (mozilla-thunderbird-1.5.0.5bg-i686-1gds.tgz) resides and you can verify it by issuing the following command:
gpg --verify mozilla-thunderbird-1.5.0.5bg-i686-1gds.tgz.asc
NOTE: You need to import the public key of SlackPack first:
gpg --import KEY