GENESIS 3 is available for download at the following links.
Source distributions code for the different packages are available here.
Mac OSX packages are available as well:
The Mac package for the developer package is available here.
The SSP package is available here.
The gshell package is available here.
Here are packages for components that need to be compiled.
Packages for 32 bit Leopard (10.5) can be found here.
Packages for 64 bit Snow Leopard (10.6) can be found here.
For instructions on how to install a developer installation from source check this document.
If you have any questions about installation feel free to contact the developers via the contact page,mailing list, or twitter.