Bug tracking software developed for the Mozilla project.
Bugzilla has also been criticised for relying heavily on MySql for its database backend, rather than using an abstract interface compatible with many different databases.
I actually found it quite easy. Admittedly, I already had Apache, Perl and mySQL installed properly. It was just a matter of running a Perl script to download and install a bunch of stuff from CPAN, creating a user for Bugzilla to access the database, and running a setup script. Furthermore, a quick search on http://rpmfind.net/ reveals that there are Bugzilla RPMs for several RPM-based Linux distributions. -- JosephDale
Now try adding additional fields. (It may have got easier recently, but when I looked last time, it was a BigBallOfMud).
Well, I don't happen to have a need to do that. Setting it up is one thing, hacking on it is another altogether. -- JosephDale
Here's something I'd love to see: http://bugzilla.mozilla.org/show_bug.cgi?id=188570
Setting up isn't that hard anymore. If you're familiar with MySQL and perl modules, it's pretty easy, actually.
For similar products, possibly simpler and also free, please see BugTrackingSoftware.