KEYWORDS

In an ebuild, the KEYWORDS variable informs in which architectures the ebuild is stable (= installable) or still in testing phase.

An example KEYWORDS setting: KEYWORDS="alpha amd64 arm hppa ia64 m68k ~mips ppc ppc64 s390 sh sparc x86 ~sparc-fbsd ~x86-fbsd"

The prefix  means it's in "testing phase" for that architecture and not ready for production usage yet.

Stabilization request
(Thanks to this blog post by Scarabeus = Tomáš Chvátal.)

Users can file stabilization requests in the Gentoo Bugzilla for packages in testing, i.e. those with  flag. If the maintainer does not respond to your request in 30 days, you can CC to arch testing teams yourself.

If a package lacks the maintainer (you can see it by seeing the section in / / /metadata.xml or the list of maintainer-needed packages in Gentoo site.) then you should also check the bugs, if it's crash-free, or there're available patches.