How to view logs in Airport Utility v6, or install 5.6 in Mountain Lion?
If you do not want (or can't) get the app out of a backup you can extract it from the installer.

Download the Airport Utility 5.6 for Lion and move the file AirPortUtility56.pkg contained within the dmg to your ~/Downloads folder. Then in a Terminal window do :

$ cd ~/Downloads
$ pkgutil --expand ./AirPortUtility56.pkg ~/Downloads/AirPortUtility56
$ gunzip -c &lt; ./AirPortUtility56/AirPortUtility56Lion.pkg/Payload | sudo tar -C / -xvf - "./Applications/Utilities/AirPort Utility 5.6.app"


The app works without issue on Mountain Lion in my limited testing so far.



If you wanted to mod the package to skip the check, if you want to easily install the package on multiple macs for instance, here's what you need :

A tool called "Flat Package Editor" to modify the file called Distribution in AirPortUtility56.pkg. To get that tool download the "Auxiliary tools for Xcode" from the Apple Dev site. It's hidden in PackageMaker.app/Contents/resources/Flat Package Editor.app. With it you can open the pkg directly :



Just drag out the Distribution file and remove these lines :

// Less than 10.8
if(-1 != system.compareVersions(my.target.systemVersion.ProductVersion, '10.8')) {
  my.result.type = 'Fatal';
  my.result.message = system.localizedString('ERR_OSHIGH');
  return (false);
}


Drag the new version back in, delete the old Distribution and save.