vvvv – a multipurpose toolkit

vvvv is a graphical programming environment for easy prototyping and development. It is designed to facilitate the handling of large media environments with physical interfaces, real-time motion graphics, audio and video that can interact with many users simultaneously. Responsible for its development is the vvvv group.

vvvv is free for non-commercial use,
commercial use requires a license.

For a detailed overview of vvvvs features read the Propaganda or see some Screenshots of vvvv for a basic understanding of what you are dealing with here. People also seem to be interested in what the faq vvvv might mean.

source: vvvv