Are there different models of the Samyang Fisheye for different cameras?

I have a Nikon D40 and Nikon D60. I'm a student and plan on continuing on in the Nikon D series as I head into the professional world and build on my equipment. I'm interested in getting a good quality fisheye lens. So far it looks like a Samyang fisheye 8mm would be the best for me right now. I've seen advertisements for "Samyang Fisheye for Canon" or "For Pantax" or "for Nikon". Are all of these lenses different? Would I be able to use the same Samyang Fisheye 8mm lens for Nikon even when I start seriously upgrading to high quality Nikon cameras like a Nikon D300s and such?

The only difference between them is that they are built for specific camera brand mounts. The one for Nikon will fit any Nikon DSLR camera.