In 2013, Adobe shut down the activation servers for Creative Suite 2 (CS2) and Audition 3.0 because they were technologically obsolete.
To assist existing owners who could no longer activate their software, Adobe briefly provided a special version of Audition 3.0 that did not require online activation, along with a generic serial number.
While finding a "free" serial number for Adobe Audition 3.0 was possible in the past, the current landscape has changed significantly. Adobe has retired the activation servers and official download links for this version, making it essentially unavailable for new installations.