An interesting look at a real-world use and development of a virtual machine, but it was more entertaining when I was reading it and thinking "Wait, was Zork the first implementation of a VM?"
Sadly, it would appear not.
You can still get z-machines and lots of old and new games from ifarchive.org (IF == Interactive Fiction). The old z-format has been superseded by Glulxe, Glulxe interpreters will still run the old .z games.
That PCW magazine Hitchhiker's Guide review (on the reviews page) was submitted by me (in about 1999).