our (CloudMakers) INDI driver definitely worked with Atik One (I have one) and to some extent worked with Atik GP (I have one as well). If it is detected but can't be connected, maybe USB rules script failed for some reason. Check permissions for device created for the camera in /dev/bus/usb/something... You can use lsusb command to find which one is it.
Atik GP is actually PointGrey Chameleon camera and only basic IIDC modes are supported by INDI driver, what limits e.g. available resolutions or framerates. If you want full support, you need to use INDIGO IIDC driver, but it will not work for you out of the box because of design flaw in Ekos. Camera reports itself correctly as PointGrey Chameleon and not as CCD IIDC as supposed by Ekos. But it should work, if you will run Atik and IIDC drivers in separate INDIGO server instead of built in INDI server. It will be also faster, because you will save one interprocess boundary.