SIMH emulates a lot of things, including VAX. You used to be able to get a Hobbyist license for OpenVMS from HP. I'm not sure whether you still can.
Note that some fields that are not marked mandatory should be treated as mandatory, esp. the one about the intended use.
Besides VAX emulators, there are also Alpha emulators you can run OpenVMS on; of interest to hobbyists are FreeAXP - free as in free beer, not open source, and Windows only - (www.freeaxp.com), and for those who want to be able to change it, the open source ES40 Emulator (www.es40.org) (disclaimer - I am the author of both of these emulators)