It's a SVT Mustang with Shelby's name & approval on it and a couple of Shelby design suggestions built in it.
It is every bit as much a real Shelby as the 1968, 1969 & 1970 Shelby's are. Those cars were mostly designed by Ford and built by a subcontractor (A.O. Smith Co.) in Livonia, MI.
If you're a nit picker then you can argue that the 1965, 1966 & 1967 Shelby Mustangs are the only "real" Shelbys as they are the only ones that were designed and built by Shelby American in a Shelby leased facility.
Then again the real Shelby purests will argue that the 1965 Shelby GT-350 is the only "real" Shelby Mustang as starting with the 1966 GT-350 they were dumbed down to save $$ and to appeal to a broader range of customers.
So call the 2007 GT-500 whatever way you want it if it makes you happy.