The recommended method of using the GoodFET is to follow the subversion feed. Every commit ought to work, but no guarantee is made as to its reliability or safety.
svn co https://goodfet.svn.sourceforge.net/svnroot/goodfet
A stable client release is sometimes posted to the Sourceforge download page. As this is very rarely updated, it is only recommended for users on Windows, which we no longer support.