iChat and Photo Booth work with other webcams that are compatible with OS X, and if a webcam isn't compatible with those applications then it most likely wouldn't be compatible with the iCamSource, either. (It's not really an application compatibility as an OS / system compatibility.)
Are you leaving Macam running when you launch Photo Booth, iChat, and the iCamSource? Macam acts as an intermediate driver between the OS and the webcam, so it does need to be loaded and running for the other applications to recognize it.