Earlier quoted context omitted.
Why? Not everything is free and open source. In fact, most of the operating systems used outside the "general-purpose" Linux realm are not (e.g. OS400, z/OS, z/TPF, AIX, Solaris, NonStop, QNX, vxWorks... even Windows Server). That said, if you're really interested, HP offers free hobbyist licenses for non-commercial use of OpenVMS, with access to the OS and compilers and usable on real hardware or SIMH.
Could you please send me the link where it says that I can get the hobbyist license. I want to give it a try.
Last time I tried (few years ago) I was contacted via email by an HP guy who asked me what architectures I needed licenses for, and then sent me a private FTP login to download all the files.
Some links to get you started:
http://labs.hoffmanlabs.com/node/23
https://www.wherry.com/gadgets/retrocomputing/vax-simh.html
If you want to emulate on SIMH I suggest you compile the latest from source (it's on GitHub).