First of all, The difference between exchess and superchess is not there. Exchess is a variant of superchess. Do not ask me the details now, but I will find out in the book I bought about superchess, made by the creator.
The game is not (really) licensed, I know the creator of Superchess. He asked me half a year ago what possibilities are there to play superchess on the internet. I immediately answered that Brainking is probably the most interesting possibility. However I programmed some things in Zillions. Now, I am very happy that the discussion started and I will tell him about (The creator, H. van Haeringen, does not have a computer). If you want to introduce superchess on the internet, then I think that you can start with the pieces: amazon (Q+N), princess (B+N), empress (R+N) and Veteran (K+N). These pieces are also used at the famous Corus Chess tournament in the Netherlands, which will be held on saturady January 28.
There are 50 pieces, from which about 30 are available as real piece. The basic pieces, which not have special function like transforming, crowning, protecting, immunity and so on, are simple to understand. Most of the pieces are combinations of each other. If you want I will post here a complete list, but it takes a while to make it.