Is there API that exchanges can use to add the coins?

The GUI is an on-top build of the main program. So depending on a compiler flag it builds a console program or our GUI program. Thus the GUI just makes calls through an API of the main program to query data and to pass through action commands. So, yes, a fully functional API is available as well as a functional console build. A small wrapper to allow connecting to the API via sockets will be developed shortly and is not a big deal.