Growl 1.3.1 .app Release Package
This repo is nothing but a build of Growl 1.3.1. The Downloads section contains a .zip file which is a Release build of the code available from Growl's source repository (see below). The specific hg revision of the build is noted in the suffix of the filename that you download.
Download & Install
Download 1.3.1 rev 5809 by clicking the icon below:
The Downloads section lists archives of all builds. To install, drag the .app file into your Applications directory.
Getting the Sources
Source for Growl is not hosted here. Importing the code into a git repo and syncing it would be too much work. Instead, you can access the original sources used to build this application on Google code hosting, at: http://code.google.com/p/growl/
Building Source Yourself
I mostly just followed a similar set of instructions to these, except I unfortunately had to figure the codesigning issues out myself. If you want to build your own copy, those instructions should work.
Growl is licensed under the BSD license. Since this is only a distribution of the original work without any modifications, you can see all of the sources from the link provided above.