Hercules is an open source software implementation of the mainframe System/370 and ESA/390 architectures, in addition to the new 64-bit z/Architecture. Hercules runs under Linux, Windows (98, NT, 2000, and XP), Solaris, FreeBSD, and Mac OS X (10.3 and later).
The installation instructions will aid you in setting Hercules up.
Site was last updated 10 years ago. Looks like an abandoned project. Does it still build?
I found a docker container that’s ‘just’ 4 years old: https://hub.docker.com/r/hermajordoctor/hercules/