It seems as though everyone has their own idea of what makes something or someone gothic. In the beginning of the subculture there actually was something more to it than the music but now there isn't. The music did come from the subculture and now that has been reversed. The intangible part of the subculture has fallen away, there is no longer a sociopolitical aspect to it, the simple fact that there is now such a thing as corp goth proves this point.
You may find these threads to be helpful:
What is goth porn? (a girl researching the subject for a class and while it does focus on the fetishizing of the subculture some of it is rather interesting and could provide some useful information for you)
Goth vs poser (gives various members' opinions of what is and is not goth)
Tumbling down the rabbit hole (how some of us got into the scene)
All grown up (how to balance an adult life with the scene)