It's in Simon's post
All of the Mac OS fixes (Minus fullscreen) are available in the latest beta:
https://powdertoy.co.uk/Download/Builds/Build-278/powder-mac32.zip
I think it's still using the stamps folder and powder.pref in the same directory ( since the last modified date is correct ) where powder.app is located at; just like before, nothing has changed.
-- Edit --
It works the first time you run it; the second time you run it, the issues are back ( prefs are not loaded, stamps are not loaded, etc. )
I have no idea why.