Ghost 14 Network backups

  I have one PC backed up using Norton Ghost 14.  I've since made up a Home Network and added two other PC's.  All three PC's are running Windows XP.  I've tried to read the Ghost 14 EULA but I can't decide if I need Ghost 14 on all three PC's or not.  Is it legal to install Ghost 14 on PC #1 and use that to back up all three PC's to an external drive?  Would I be better off buying the newer Ghost 15?