The copy I have was made for me by the Perry-Castañeda Library at the University of Texas. They had recently placed their copies of the Baltimore Sun in an area or online site accessible only by UT staff, faculty, and students, of which I was none. Since I only wanted the one article from that paper, a gentleman in the library staff kindly accessed their system and made a copy of the article for me. Unfortunately, the fine print on the border of the copy says the copy is copyrighted. Also, in order to be able to photograph parts of old newspapers, I had previously signed a statement at the University of Texas that I would not reprint or publish photos I might take of newspapers in their collection. I do not post my photos or Xerox copies I make of old newspapers on microfilm either, figuring the images are copyrighted by the makers of the microfilm.
However, the words themselves of the article are not copyrighted. Although I could not find a copy of that issue of the Sun online, I was able to use the words of the 1861 article themselves, that are no longer under copyright, to search online for other newspapers that reprinted the article.
I found the entire article in the Library of Congress's Chronicling America web site reprinted word-for-word in the Newbern weekly progress of Newbern, NC on April 30, 1861, Image 2. I posted a link to that newspaper in my post 328 of this thread along with links to two other newspapers that had reprinted all but the final paragraph of the Sun article [Post 328].
Here is the link to the Newbern newspaper that contains the entire Baltimore Sun article. The words in the Newbern newspaper exactly match the words of the copy of the Sun article provided for me by the University of Texas. [Newbern weekly progress copy of the entire Baltimore Sun Article].
On another point, "Copyrighted"? Something 150 years old is copyrighted? Even with all the relatively recent changes that make copyrights last 80 years, the copyrights are expired.
I'm not sure what angle they can claim to assert that they own any sort of legitimate copyright. But if you signed an agreement, as a man of honor, you will have to abide by it, even if it's silly.