it's maybe the complete source. I got access to it, and the files are full of "Amiga Confidential" notifications in the C source files.
Only a coder can say. Contact Toni Wilen, and let him check. He will say if it's complete or not.
EDIT : there is no word about Cloanto, so the archive has been leaked by one of the original amiga engineers, there's no other possibility.