The people who preserve vintage software typically respect boundaries in order to avoid cases where the copyright holder would be financially harmed. It is not a perfect guarantee, but it is a reasonable one.

Hardline stances usually cause more harm than good anyhow. I remember collecting Apple II gear in the late 1990's and early 2000's. The people saying that any form of copyright infringement was bad were either ignored or flamed since a lot of people just looked at their collection of software from the late 1970's and early 1980's and said, "we're at risk of losing this if we don't make it available, and the copyright holders won't lose anything if we do make it available." Which wasn't strictly true since there were some software developers who created software in the early 1990's who were still selling it. Unfortunately their absolutist attitude did not earn them many allies, so it became a lost cause.