The imageio-ext-gdal-bindings*.jar included with the gs-gdal extension is an older (~1.9.2) version of the GDAL bindings. This will cause classloader conflicts if you try to use it with newer versions of the bindings. It wouold be more correct to rely on the bindings jar that comes with whatever version of the GDAL native libs the user is using.
I have a pull request here which removes the old binding jar from the geoserver release build.
The 1.9.2 gdal native artifacts linked from the geoserver docs include this bindings jar, so it is still available to anyone who follows those instructions.
Does this approach seem correct? Is there any reason we should be including the bindings jar in the gdal plugin?
Torben