As I understood how the nVidia driver works, this is exactly the method. There is a GPL'd
piece that integrates into the kernel and creates the interface to the binary driver. Just
like ndiswrapper works, in fact I thought that the nVidia Linux driver was created because
ndiswrapper showed them how to integrate a closed source binary driver into the kernel.
I also thought this was one of the reasons certain developers hate ndiswrapper so much, they
started the whole trend to the binary blob in the kernel thing.