Preliminary instructions. Pretty sure I covered all the steps here.
To get the drivers installed under Snow Leopard:
1. Download the drivers from the D-Link website and mount the DMG file so it shows up like a drive on your desktop.
2. In that "drive" is a file named "D-Link DWA-160 Install.pkg". The icon is a cardboard box and you probably wont see the .pkg extension. Drag this file to your desktop and close the Finder window.
3. Right-click (ctrl-click) on the package file on your desktop and pick "Show Package Contents". This will open the pkg in a Finder window.
4. Open the "Contents" directory. Open the "Resources" directory.
5. Right-click (ctrl-click) on the "postflight" program. Choose "Open With" then "Other". In the dialog that pops up, scroll down to TextEdit. Select TextEdit and click Open.
6. You'll get a dialog saying "postflight" is a Unix application downloaded from the Internet. Click Open.
7. Change the first line from:
#!bin/sh
to
#!/bin/sh
8. Save the file and quit TextEdit.
9. Run the installer package from the desktop. You'll still get the kext warning, but you can ignore it (truthfully, you always could). But, this time the installer will complete and make you reboot.
10. When your computer comes back up, the DWA-160 utility will load but it wont detect any network cards.
11. Open a terminal. Type:
sudo kextutil /System/Library/Extensions/AtherosOtusMac.kext
(hit return)
12. The DWA-160 utility will spring to life. Go through the normal setup steps of opening Network preferences and fiddling with everything.
13. After you've played with your new toy a little bit, go back to that terminal window and type:
sudo touch /System/Library/Extensions
(hit return)
14. Your drivers should now load every time you reboot.