The version numbers of gnats 3.x is somewhat confusing, because 3.1xx is newer than 3.2.
Version 3.2 was released in 1993 (I never tried it, but it is said to be "really broken"). A lot of new features have been added since 3.2, including multiple database support and customized fields. Among the contributed software are comprehensive WWW and Tk based front-ends.
The latest 3.x release is 3.113.1. It is deprecated due to security concerns and lack of maintenance.
gnats 4.0 was released in August 2003, and 4.1 was released in March 2005. All released versions are available for download at http://ftp.gnu.org/pub/gnu/gnats/.