Os X - Dj Four Tracks Simultaneously (gpl!)

General Discussion
1

DeKstasy is a DJ application for Mac OS X. It provides automatic beat-finding and seamless beat-locked playback of up to four tracks simultaneously, contains a built-in mixer, and is so rock-solid you won’t believe it’s free software.

http://www.sonophile.com/
http://sourceforge.net/projects/dekstasy/

GPL, like woah.

2

Neat.
I think I came across this once last year but it wasn’t open source then. I like the midi clock output :)