VPython is ideally suited for visualizations of simple physical systems, but it isn’t designed for movies for classroom lectures. It isn’t hard to take advantage of a variety of OSS tools to make movies on OSX, though.
Here are some examples:
Pendulum going through π radians
Pendulum going through 2π radians
Particle moving on an energy surface
Wave transmission: heavy to light
Wave transmission: light to heavy
Use VPython to make your animation.
At every step in the animation (i.e. every re-rendering of objects) take a screenshot (/usr/sbin/screencapture) and save the file.
Use Imagemagick to crop out the image of the VPython animation and turn it into an animated gif file or movie file (using QuickTime).
is some sample code used to make a movie.