KCalendarCore is a library to provide access to and handling of calendar data.
It supports the standard formats iCalendar and vCalendar and the group
scheduling standard iTIP.

Utilities for interacting with KCModules

kcontacts is a Qt5 based library which provides an API
to access address book data stored in different formats.

KDE Daemon

KDNSSD is a library for handling the DNS-based Service Discovery Protocol
(DNS-SD), the layer of Zeroconf that allows network
services, such as printers, to be discovered without any user intervention or
centralized infrastructure.

KEmoticons

A library for extracting file metadata.