How can I open a file with extension DAA on Mac?
According to this reference, .daa is an extension related to the PowerIso application. This 2008 MacWorld article suggests an open source application - DAA Converter for OS X. The app page states:


  DAA Converter is a free utility for converting DAA &amp; GBI disk images
  to ISO format so they can be accessed on your Mac. 
  
  DAA Converter is a native GUI application which wraps the command-line
  tool, DAA2ISO/GBI2ISO, by Luigi Auriemma.  It runs on Mac OS X 10.3
  Panther or later.


I don't have any .daa files to test with, so I can't verify that this utility works. However, it's a GPL freeware app, so it wouldn't hurt to give it a shot.