I've looked into porting gPhoto (
http://sourceforge.net/projects/gphoto/) over to Mac OS X. gPhoto is a command-line app that supports an impressive array of cameras, including my son's JamCam 3.0. gPhoto compiles out of the box with no problems.
However, for USB communications it relies on libusb
(
http://sourceforge.net/projects/gphoto/), which has not been ported to Mac OS X / Darwin. I've looked into it, and libusb is a really simple library that shouldn't be difficult to port. But I haven't had the time to do more than a preliminary investigation. If I actually do get a working application, though, I'll announce it here.