For those interested, I finally found the solution.
According to the AMD developer site, GDM must be configured to allow remote X connections across SSH directly into the local :0 display (if using Stream SDK over SSH). The xhost program is used to configure these permissions through a GDM configuration file. The problem was that xhost was not installed on the system.
Being a Ubuntu Server installation, X was not installed by default and a basic gnome environment was installed with aptitude. The minimal Gnome installation for Ubuntu Server does *not* include the xhost program. Unfortunately, the call to xhost in the GDM configuration file referenced by the AMD developer documentation fails silently, so there is no indication of a problem, other than Stream SDK apps not running without root.
The solution is to install the x11-server-utils package on Ubuntu (other distributions should have a similar package, if xhost is not installed by default). Now xhost will properly run when GDM starts and Stream SDK applications can be used without root permissions.
I believe the Remote Access documentation on the AMD developer site should be updated to reflect two points:
- Ensure xhost is installed on the local system
- Newer AMD drivers seem to use /dev/ati/card* instead of /dev/dri/card* as mentioned in the documentation.