The hash file is read by get-form-hash in bbs.scm. It is called for the value of the ornamentum field by make-post-form and make-thread-form in templates.scm. The ornamentum field is read by validate-form in bbs.scm as the hash of the let. Validate-form then proceeds to do precisely nothing with the hash value. After the size checks it only cares that the message and name fields are empty. Therefore it appears that the hash/ornamentum is intended as another antispam measure that is yet to be implemented, and is currently a no-op.