Bocfel

Bocfel is an interpreter for the Z-machine, made by Chris Spiegel.

It fully supports Z-machine versions 1-5, 7, 8, and contains partial support for version 6.

Features

Almost no platform-specific functions are used—and those that are used are optional—so almost any system with a recent C compiler should be able to build and run Bocfel.
Makes use of Glk for input/ouput, with complete support for Gargoyle; a non-Glk "dumb" interface is also available.
Support (assuming a font with Unicode box-drawing characters) for the character graphics font used by Beyond Zork.
Unicode support.
Multiple undo in almost all games, including those which do not natively support it.
Full control over command recording, transcripting, and command-record playback.
Rudimentary "cheating" support, designed to disable hunger and thirst daemons.