To make GeneWeb work, you have first a manipulation to make. I am sorry, the installation is not automatic, but we don't find a way to make it easier. We are working at it.
This manipulation has just to be done once.
Afterwards, just double-click on "GeneWeb" to start the application.
MANIPULATION FOR INSTALLATION
Here is what you have to do. Warning: in your MacOS X version, the messages may be different. The general idea is to attach the file "GeneWeb" to the "Terminal" application: