Then the patents are not a restriction (they might be useful as technical reference material). The only real restriction becomes the copyrighted intellectual property (Kickstart, AOS, etc.).
So, is there a way to uncover the details of a old patent?
The old patents are for an implementation of an idea, since we don't want to sue that implementation anymore, I doubt there are any chip fabs left in the world that could build the original chips anymore, they are valueless... Best just do what has been done before with UAE, MiniMIG and Jens cloneA projects where you simply duplicate the functionality.
Yeah, the intellectual property is more difficult... Kickstart and AOS are both protected by copyright... but there is no law against cloning them... and thus AROS...