Unfortunately WYSIWYG Web Builder cannot run on the Mac and its source code cannot be ported to the Mac because its uses many Windows technologies that work very differently on the Mac.
HOWEVER we decided to create a complete new product designed from scratch specially designed for the Mac, but with the possibility to port it to Windows and Linux. We called it Quick 'n Easy Web Builder.
And although it does not use the same project structure and projects are not interchangeable with WYSIWYG Web Builder, we have implemented the best features of WYSIWYG Web Builder into Quick 'n Easy Web Builder.
You can check it out here:
http://www.quickandeasywebbuilder.com/