It is the work of Drew McDermott, although many of its facilities are descendants of tools described in
Eugene Charniak, Christopher Riesbeck, Drew McDermott and James Meehan 1987 Artificial Intelligence Programming, (2nd edition)}}. Lawrence Erlbaum Associates
The latest version should be possible to download by using repository clocc.cvs.sourceforget.net:/cvsroot/clocc and checking out clocc/src/ytools.
The documentation (over 50 pages long) is available separately.