iCamSource requires an MJPEG URL for each IP camera it displays. If your video server has a unique URL for each camera, then you would be able to access each one in iCamSource.
From searching around, it looks like Axis video servers (some of them, at least), can use an argument in the URL for the camera, like this : "http://<Camera_Address>/axis-cgi/mjpg/video.cgi?resolution=320x240&camera=1"
If your video server supports that argument, you should be able to enter different values for the "camera" variable to access different cameras