Let's say you want to do realtime editing and effects -- the kind of stuff you get with high-end Avid systems, or more modest applications like Adobe Premiere and Apple Final Cut Pro? You're going to spend thousands. If you're really serious, the costs can run into six figures, easy.
Well, not any more, thanks to Jahshaka, "The World's First OpenSource Realtime Editing and Effects System." The brainchild of Jah Shaka, a native of Kingston, Jamaica and a music industry veteran, the project has (at this writing) reached the Alpha stage, and runs on Linux, Irix, Windows and (soon) OS X. Right now the modules include Effects, Animation, Editing, Paint, Text, Player and Compositor.
Jahshaka is developed in the OpenML programming environment, which supports capturing, transporting, processing, displaying, and synchronizing digital media (2D and 3D graphics, audio and video processing, I/O, and networking).
And it's GPL'd too.
<http://www.khronos.org/openml/>
Note: There are some very nice full-size screenshots at the site.