Ah, yes, the alt vine dragon. I don't think you have to inbreed to get that, though I imagine it's easier to get one if you're not worried about inbreeding.
I haven't ever really gone back to the game. I can see from other people's sig lines that there are new types of eggs and dragons available now, but that whole aspect of the game is based on camping on the Cave page and clicking like mad, or begging someone else to get a "rare" egg for you. Not my idea of fun.