I cant see how any of it would matter at all. Most everything Amiga related has expired patents. What could any legal team even do at this point?
You don't understand the legal situation. "Patents" and "copyright" are two different things with different implications. A "patent" is a published idea, with the possibility to use the idea in third-party products (here, as in "software") by license granted by payment of money. A patent does not apply to a "code as such", but to the algorithm the code implements. Those have run out.
The "copyright" is the code "as is", the particular implementation of an "IP-right" as stated in a patent. And the copyright did run out. It usually extends 30 years after the death of its creator, or even 70 years now with the Mickey-Mouse law in place. You can certainly re-implement the same algorithms(!) AmigaOs is based on without violating the copyright. You could possibly violate a patent by that, but as you state correctly, those have run out. You should then be aware that the copyright holders (not IP-right holders!) may look very suspicious at you to ensure that no copyrighted code has been used.
No, you cannot, legally, do anything with these leaked sources. They cannot be exploited without permission of the owner of the copyright. You can at best re-implement *without* looking.
And no again, simly typing down the code from the stolen source does not make the resulting work legal, it would still be a derived work. If you want to be perfectly safe, "don't use, don't look, create all yourself".
The community of developers that can even make use of this stuff is so small that it should be a no brainer to let them look and give back.
Look, I would not even try looking for this stuff in torrents and so on. First of all, you do not know in which condition it is and whether it is any useful, i.e. reflects a compilable and stable state of the Os.
Second, it is not administrated and maintained. So even if you fix a bug, who tells that the fix can be passed along and is not lost, or confused because another person makes another "fix" or "improvement".
Third, if you really want to, there is of course an administrated AmigaOs on a specific version control system if you know where and how and whom to ask. However, as stated above, if you know, and if you look, you should be aware of the implications. If you use such code, it's copyrighted, and by publishing work based on this code, you are infringing rights of third parties which may get you into serious trouble. With knowledge comes responsibility.