Our website provides a free download of Uzu 3.1.2 for Mac. The application lies within Design & Photo Tools, more precisely Viewers & Editors.
From the developer:
Uzu is a kinetic multitouch particle visualizer that lets you create a vortex of color and motion.
You may want to check out more software for Mac, such as TVPaint Animation, Cuadro or Resize Now, which might be similar to Uzu.