Open Genera is the Genera OS which used to be run on Symbolics Machine.
Open Genera is the Genera OS running in a virtual machine.
 http://www.textfiles.com/bitsavers/pdf/symbolics/ (mentioned on the wiki)
One can buy an official version of Open Genera at:
This is usually understood as enterprise-speak for "we don't want to give you a price, and if you have to ask, you can't afford it."
"Thank you for your request for information about Symbolics and our products. Our Open Genera software for HP/Compaq/DEC Alpha workstations running Tru64 Unix costs $5,000 for a single CPU license. There is an academic discount for students and teachers that brings the price down to $999. You should have a 300 mHz or greater Alpha workstation with at least 500 MB RAM, 4 MB cache and 1 GB of available disk space. Besides selling Open Genera and maintaining the installed base of Symbolics machines, we
also sell refurbished Symbolics hardware. There is no hardcopy documentation, but there is complete documentation available on the hard disk of each system."
As of a few months ago when I checked, he said they no longer sell refurb hardware, keeping the remaining stock for service contracts/warranty work/etc.
Here's some instructions on setting it up:
Buy the Alpha version or ask whether it is possible to buy the new version.
One would expected that they would bother to put up a better web site.