It's more to it than simply open source it. I work for AOL, and know some folks who worked on Winamp on a personal level. Winamp has proprietory licenses for some of its codecs for every install AOL pays licensing fees which it does recoup via other services (such as search agreements with GOOG or Shoutcast major partners). If it were to AOL to open source it, it need to strip our those pieces, translating into few months of work on the clock.