Not quite the same, but if you want to replace ghee with something vegan, try avocado or coconut oil. There is vegan ghee (made from palm oil I think?) but it's bad for you the same way old timey margerine is bad.

Incidentally, unprocessed red palm oil could be a nice replacement, but it has a characteristic earthy/almondy taste. I love it on fish dishes but it's not the taste you expect from Indian food I think.