Well, we do have a rather early fully legal 1981 copy of the system, and one or more illicit but no one seems to care copies of much later Symbolics systems (don't know if those included source, though). So that in part an issue of software archaeology, when we can also ask most if not all of the people involved about details.

And I fully agree the focus should be on the software, as I hope I made clear in other comments in this topic.