Waves 7, 8 and 9 Audio Units are not compatible with Audacity.
If VST or AudioUnit effects are not needed in Audacity, force quit Audacity, then open Finder, Go > Go To Folder and open ~/Library/Application Support/audacity/ .
Open audacity.cfg (or create it if it does not exist) then add or edit it so you have only the following lines:
NewPrefsInitialized=1
[AudioUnits]
Enable=0
[VST]
Enable=0
Rescan=0
Then try launching Audacity.
If you have some earlier version of Waves, then you could try licensing it. Audacity loads plug-ins at launch, rather than when you use them, so Audacity will relay the nag message from Waves every time it launches. Or just disable AU and VST plug-ins anyway using the above code in audacity.cfg.
Gale