A very strange thing; GIMP opens as a single layer?
I've never had this encounter with PSD files before; usually they open layered just fine. Could somebody else with an Adobe CC account confirm if this upload has the ten layers he promised? Because it all ends up being the same can of beans for me... not that it isn't good in its own right, just not what I expected.
My only guess as to why this is happening; GIMP has no trouble reading layers from the default group, but it may have trouble reading any more groups, despite GIMP's capability to read layered PSD files; GIMP may not be able to read multiple layer groups. Not sure, as I don't feel like pirating PS CS5 to find out.