Earlier quoted context omitted.
It's the same problem z/OS has: There's no hobbyist community so it remains obscure. Yes, you can run 1980s-era System/370 software under Hercules, but IBM keeps anything remotely modern under lock and key even though you'd think it would benefit IBM to have people indoctrinate themselves into the Blue Worldview.
It might not be legal, but it isn't hard to find newer versions to download if you know where to look – z/OS 1.11 is floating around, it is from 2009, so still rather old, but a lot newer than the 1970s. Also you can find some OS/390 and MVS/ESA versions from before that (1990s vintage). If someone privately runs it for purely non-commercial purposes – I myself never have, but some people do – I think it is rather un…
Never got it installed, but yeah, it's easy enough to find.