If after connecting the camera with a USB cable, if it is not working with dslrBooth, try the following:
Make sure there are no other applications such as EOS Remote running on your Mac. Also, make sure that there is no software set to auto start when the camera connects.
Open the Mac app "Image Capture", choose your camera on the left side and choose "no program" from the little drop down menu on the lower left side. This way the EOS Utility will not start and the camera will be ready for dslrBooth.