Uzu 3.2.1 for Mac was available to download from the developer's website when we last checked. We cannot confirm if there is a free download of this app available. Uzu for Mac lies within Design & Photo Tools, more precisely Viewers & Editors. The actual developer of this software for Mac is Jason K Smith.
From the developer:
Uzu is a kinetic multitouch particle visualizer that lets you create a vortex of color and motion. It is a sort-of math-physics-art-toy for anyone who ever loved spirographs, fireworks, planetariums, lava lamps, light sabres, pen lasers, tesla coils, Christmas lights, or graphing calculators. The points of light will shoot across the screen and fly to your command, twirling in a vortex of color and motion.
You may want to check out more software for Mac, such as Movie2Shot, TVPaint Animation or Cuadro, which might be similar to Uzu.