Best Practical RequestTracker was released on Aug 17, 2011.
Portage still has only the oldish rt-3.6.7 in tree and an ebuild was proposed for 3.8.8 (see bug #235914).
Installing RT on a gentoo system is a pain if you want to keep it 'clean' (ie, manage as much as possible via portage) due to numerous dependencies (CPAN and others). It would be great to have an ebuild for the new rt-4 branch.
*** This bug has been marked as a duplicate of bug 235914 ***