You can definitely have more than one record returned from V$INSTANCE, but only if you are having paralel server (OPS/RAC) configuration on that database. One record per instance that has database mounted.

The script you are refering to (http://www.dbasupport.com/oracle/scripts/Administration/Audit/ ) has a totaly different isue, though! That script was obviously written for Oracle7 or earlier and will not work in Oracle 8.0 or any later release, since starting with Oracle8 the view V$INSTANCE has totaly different structure. With Oracle7 you allways got more than one row from it and hence the WHERE clause in that script.