To install Dibbler in the Gentoo system, add following line to 
the /etc/make.conf file:

PORTDIR_OVERLAY="/path/to/this/directory"

Then issue following command:

emerge dibbler

Dibbler will be compiled in a Gentoo way.

Interesting fact: This ebuild was uploaded to the bugs.gentoo.org
(see bug #76084, http://bugs.gentoo.org/show_bug.cgi?id=76084).
There's a distinct possibility that it will be incorporated to the
main Gentoo portage in a near future.
