There is currently no official method of hiding the iCamSource icon on your Mac.
An "unofficial" way would be to right-click the iCamSource application in your Applications folder, select Show Package Contents, then open the Contents > Resources folder and renaming or moving the iCamSourceStatus_Running.png file. Then, when you run the iCamSource and Start it, no icon will appear in the menu bar, although there will be a blank space still visible that you can click on to access the iCamSource.