Portage
Portage is similar to the BSD package management system called ports; in fact it was originally designed with FreeBSD’s ports in mind. Gentoo’s Portage system works similarly to Debian’s APT. Portage is written in the Python programming language, and is the main utility that defines Gentoo. The Portage system offers the use of “USE flags,” which allows users to indicate which software features they would like to include while building packages.
There is also a “Gentoo for Mac OS X” project which allows Mac OS X users to use Gentoo’s Portage to install packages, in a similar way to the one provided by Fink. Although still a work in progress, this project can coexist with Fink because it uses the same environment as Mac OS X instead of creating a new one.
Portability toward other operating systems, such as BSD-derived ones, are under active development on Gentoo/ALT project. The Gentoo/FreeBSD project already has a working release, while Gentoo/NetBSD, Gentoo/OpenBSD and Gentoo/DragonFly are being developed.