Ok, I see your point better and agree that that would be the intended meaning of the prejudice clause you cite; also that the surveyor probably would not want it sold to, or used by, a third (or outside) party some time afterward for decision making. I suspect, however, one intent there (CYA) is to make it clear that the surveyor is not liable for the consequences of any decisions made by third parties on the basis of a dated survey that the party did not purchase from him directly. So who, still, is the use statement directed to?:
and may not be used for any other purpose or relied upon by any other person. If I sold a survey document it then becomes the buyers decision to "rely" on it; not mine. It'd be more clear if the statement carried the same kind of explicit no-nos of, say, copyrighted materials, about resell or distribution of the document, etc. Of course, the seller of a survey document to a third party would be breaking the "in confidence" aspect of the document as you cite it. The seller/owner of the boat might have recourse if done w/o his permission and he found out about it later where it caused him to perhaps lose the sale of the boat. In the cases I mentioned above the respective owners made the documents available. Also, those "negotiations" took place in Canada, not in the U.S.; so there may be a difference there with the legalities. Still, I agree now that the selling of a survey document to a third party w/o interest at the time of the survey and especially w/o the consent of the owner of the boat, would not be a wise, good, or fair thing to do.
