Installing snapshots and live ebuilds are only available through kde overlay, so first thing is to install it:

# layman -f -a kde
For more information regarding overlays, please read the Overlay Guide

During testing phases KDE upstream provides snapshots taken from the git source repositories. Beta and Release Candidate KDE releases are following the snapshot model below:

KDE SC is Open Source, with its code being available for browsing through KDE QuickGit, and for public checkout. Gentoo, as a source based distro, has the ability to provide live ebuilds that checkout the code either from the latest branch or from trunk. Currently, we provide 4.9.49.9999 ebuilds from 4.9 branch and 9999 ebuilds from trunk.

Users with stable systems have to keyword the packages to proceed. We provide a package.keyword file in kde overlay, which we'll have to symlink to our package.keywords directory:

# cd /etc/portage/package.keywords
# ln -s /path/to/overlay/kde/Documentation/package.keywords/kde-4.9.49.9999.keywords .(for 4.9 Branch)
# ln -s /path/to/overlay/kde/Documentation/package.keywords/kde-live.keywords .(for KDE Trunk)

The installation can be done either by using the meta packages or by using sets.

# emerge -av kde-meta (contains all of KDE modules)
# emerge -av kdebase-meta kdegames-meta (installation of chosen modules only)

(For KDE SC 4.9 Branch)
# emerge -av @kde-4.9 (contains all of KDE modules)
# emerge -av @kdebase-4.9 @kdegames-4.9 (installation of chosen modules only)
(For KDE SC Trunk)
# emerge -av @kde-live (contains all of KDE modules)
# emerge -av @kdebase-live @kdegames-live (installation of chosen modules only)

See the Using Sets section for more information.

One of the new features provided by Portage 2.2 is sets, which can be used as replacement for the metapackages. In general this is not recommended, however it may provide advantages if you are using live ebuilds. Sets for the kde packages can be obtained from the kde overlay sets directory or grab them as a tar.bz2 archive and put the ones you like in /etc/portage/sets -- you can browse the list of sets provided by the KDE team in the overlay by using the first link.

Amongst others, there are sets for each KDE tarball - @kdeaccessibility, @kdeadmin, @kdeartwork, @kdebase, @kdeedu, @kdegames, @kdegraphics, @kdemultimedia, @kdenetwork, @kdepim, @kdesdk, @kdetoys, and @kdeutils. There is also a set of sets (the equivalent to the old kde-meta package) @kde, and the same for specific versions @kde-3.5 and @kde-4x, a set for KDE deps @kdedeps, a set for optional packages @kdeoptional and a set for the split qt packages @qt-split.

One can install the complete KDE by running emerge -av @kde. The specific version equivalents are very useful to uninstall an old version, e.g. emerge -C @kde-3.5, or to reinstall all packages from a specific version, e.g. emerge -av1 @kde-4x.

With new KDE there is new translators effort in Localization instead of Internationalization. This cause some confusion, but don't worry; just the name has been changed.

For KDE 4 and Calligra:
# emerge kde-l10n
# emerge calligra-l10n