Providing that you bought Pro from the official site Lime Wire » Official Website & Free Download, BitTorrent « ...

If your Pro benefits are still current (ie still within the 6/12 months that you bought Pro for) then you can go to your Pro personal download page & download a Mac installer.

If you haven't saved the link to your personal download page, but your Pro benefits are still current, click on the link below & enter the email address that you used to buy Pro.
Lime Wire » LimeWire PRO Lookup

If your Pro benefits are out of date, or you bought from a site other than the official site, you'll have to pay again for Pro.