If you want to pull things in from a different installation, find the global that you want to use, and then instead of
my $db = $DB->table('Category');
use this (replace /path/to/admin with the path to the admin of the other installation):
use lib('/path/to/admin');
my $db = GT::SQL->new('/path/to/admin/defs')->table('Category');
my $db = $DB->table('Category');
use this (replace /path/to/admin with the path to the admin of the other installation):
use lib('/path/to/admin');
my $db = GT::SQL->new('/path/to/admin/defs')->table('Category');