Copyright is a thorny issue and it is not clear to me where the distinction between quoting excerpts and infringing copyright occurs.

QUOTE:
I will hazard that MathCAD has a license to publish Roarks formulae. If this website accumulates too many workbooks covering Roarks, then it becomes an "accidental" publisher of the book

I'm not sure this is a big issue. Faithfull reproduction of sections of the book may be more problematic but I'm not sure that any copyright can be claimed for Formulae themselves since those contained in Roarke are most often based upon work published in research papers rather than the author or publisher of the book. The copyright owner in that case would be the original author of the work.
The content of scientific papers is often quoted in books and other papers. It is usual in those instances to reference the source of the information. Also I'm not sure that anyone can claim ownership of a mathematical formula that can be derived from first principles by anyone with sufficient nous to do it.

Something similar, I think, can be said for standards i.e. publishing design sheets to satisfy the requirements of a standard is not neccesarily the same as copying the standard itself. As you infer, problems could arise if the worksheet is such that the codes become redundant or sales are damaged I guess.

Information on UK copyright law is published here http://www.copyrightservice.co.uk/copyright/p01_uk_copyright_law