KDE PIM is a package that contains personal information management tools.
The KDEPIM team develops the main application Kontact with all its plugins like KMail, KNode, KOrganizer, KAddressbook, Akregator, KJots and others.
Much of the infrastructure of KDE PIM has been moved to kdepimlibs module as a framework for all KDE applications. Therefore we have two main modules within the KDE SVN: kdepim and kdepimlibs. The latter contains code that provides public APIs.
Current development focus as of January 2009 is on the Akonadi service and porting existing applications to Akonadi and KMime and other frameworks.
If you're looking into starting KMail development, have a look at the list of KMail junior jobs.
The KMail handbook is currently being rewritten, for more information look at the documentation wiki page.
The KDE PIM 3 branch is frozen and no longer actively maintained. Use the KDE 3 enterprise branch for a version of Kontact that is still being updated.
Kontact is the primary Kolab client. There are different release cycles for the Kolab clients and for KDE, and therefore there are so-called enterprise branches in SVN where the Kolab versions are maintained. Changes in the enterprise branches are regularly merged back to SVN trunk. The enterprise branches are maintained by KDAB.
More information about the enterprise branches can be found at:
This list is quite incomplete.