I can try . . . but the LW installer for OSX doesn't use Stuffit.

The one on your download page should be for MacOSX, and downloads to your desktop as "LimeWireOSX.dmg", which you can double-click and Disk Copy (from your Utilities folder) will mount it as a disk image.

Can you let me know the file name that shows up on the desktop, and which version of OSX you are using?

Cheers