The widgets are running natively on the client. There's no interpretation / JIT layer between the two like with a web stack. All you're doing with OpenGL rather than Win32 is drawing your widgets to the graphics buffer directly rather than using Win32 libraries to draw the widgets. So, to go back to the original comment, it is a "native GUI" it's just not calling Microsoft or Apple's toolkit libraries.

This might sound like nitpicking, but you also have to bare in mind that it's not always as simple as saying "You want to write a native app, use Win32 or Cocoa". Half the time developers are running wrappers around the toolkits such MVC, .NET and wrappers to allow non-C et al languages to call C libraries. And even if you do want to directly call the "native" OS libraries, often there's more than one to choose from, eg on Linux things gets pretty complicated as there's several toolkits available (GTK, Qt, Motif, etc) and then a multitude of version of many of those libraries. Granted this doesn't solve the "many standards" problem, but at least it's a single dependency that runs natively on the client and draws directly to the graphics buffer - which has got to be better than the plethora of other cross platform implementations out there.