Their online emulators are explicitly authorised via a DMCA exception granted by the Library of Congress, c.f. https://archive.org/about/dmca.php

> Following deliberation, the Copyright Office ruled in late October 2003 that four exemptions should be added to the anti-circumvention clause of the DMCA, to be valid until the next Copyright Office rulemaking in 2006, including two that are related to the Internet Archive's original comments: >

> Computer programs protected by dongles that prevent access due to malfunction or damage and which are obsolete. > Computer programs and video games distributed in formats that have become obsolete and which require the original media or hardware as a condition of access.