Public Domain / Terms of service

Hello! As an amateur genealogist and a subscriber to Ancestry and Newspapers.com I have became interested in reproducing some of the old newspaper items in a book form. Because these items are pre 1920, they are considered "public domain". However, the terms and service agreement seems to forbid any commercial use from it's collections without their written permission. Without giving away my idea, I'm gonna describe something that is very close to what I have planned. Let's say I want to publish a book with editorials submitted by readers published in these old newspapers. Perhaps during one month out of the year, hundreds of readers would write editorials about a common issue. Since I find these letters interesting because they were problems that were of grave importance way back in the early 20th century, i'm thinking other will as well. Anyway, the terms of service require me to ask permission from Ancestry who owns Newspapers.com. Incidentally, I do not plan on using the actual images but to re-type the letters and indicate the newspaper the were originally published in. My plan is to do many books from lots of newspapers. My question is: Can they legally deny me the right to do this since they are in the public domain?