D-Bus is a message bus system, a simple way for applications to talk to one another. In addition to interprocess communication, D-Bus helps coordinate process lifecycle; it makes it simple and reliable to code a "single instance" application or daemon, and to launch applications and daemons on demand when their services are needed.
The Telepathy project aims to provide a unified framework for all forms of real time conversations, including instant messaging, IRC, voice calls and video calls. It uses the D-Bus messaging system to provide a simple interface for client applications, allowing them to quickly benefit from Telepathy's functionality.
Mission Control, or MC, is a telepathy (chat and voip framework) component providing a way for "end-user" applications to abstract some details of low level telepathy components such as connection managers.
Various games are divided into two logical parts: engine and data. Often the engine and data are licensed in different ways, such that only one half can be distributed in Debian.
game-data-packager is a tool which builds .deb files for game data which cannot be distributed in Debian (such as commercial game data).