Assuming that the materials he is copying were once copyrighted, here is some information you and MH may find interesting. I was under the impression that copyright laws only lasted 50 years but it seems they last much much longer. However, for the older materials MH is using it is likely copyright had expired. The following info I found at the US Copyright Office web site.
"The term of copyright for a particular work depends on several factors, including whether it has been published, and, if so, the date of first publication. As a general rule, for works created after Jan. 1, 1978, copyright protection lasts for the life of the author plus an additional 70 years. For an anonymous work, a pseudonymous work, or a work made for hire, the copyright endures for a term of 95 years from the year of its first publication or a term of 120 years from the year of its creation, whichever expires first. For works first published prior to 1978, the term will vary depending on several factors."
"Under the 1909 copyright law, works copyrighted in the United States before January 1, 1978, were subject to a renewal system in which the term of copyright was divided into two consecutive terms. Renewal registration, within strict time limits, was required as a condition of securing the second term and extending the copyright to its maximum length."
"• If a copyright originally secured before January 1, 1964, was not renewed at the proper time, copyright protection expired at the end of the 28th calendar year of the copyright and could not be restored."