Andrew,
All those results you saw were for various features in NetBackup.
With *nix, you have to patch each feature that you have installed.
So, if (for example) you have NetBackup with the Oracle and DB2 feature (there are tons of other features to choose from), you will have to patch the following:
NB_CLT__51_5 (this is the clients patch; you have to install it on your master before you can patch the core install; this install will automatically kick off the core install patch when it finishes, provided that you have the patch files extracted in the same location)
NB_51_5 (core NetBackup patch)
NB_ORA_51_5 (patch for Oracle agent)
NB_DB2_51_5 (patch for DB2 agent)
Without any agents, you just need the first 2 patches. Un-tar them in the same location and run the Vrts_pack.install script. Choose the CLT patch first and let it run. It will automatically kick off the other patch when it completes.
Obviously you will want to have your NetBackup services shutdown before upgrading: /usr/openv/netbackup/bin/goodies/netbackup stop
$0.02