Making all those gnutella p2p programs, was the original aol gnutella 0.56 source code released? Is there a gnutella protocol out there?

I really liked the original gnutella 0.56 p2p program. It was a full tiny 56kb program. Now all these today's gnutella programs are 4MB download setup files, then 10-20MB installation. Why can't someone write a tiny gnutella p2p program?