Gnusto is a JIT compiler and virtual machine for the Z-Machine, originally written by Thomas Thurman.
Thomas Thurman originally designed Gnusto as a Mozilla/Firefox extension for a full Z-Machine interpreter. He and a few others worked on it for several years, but stopped in 2005.
In 2008 Atul Varma used the VM engine code and built a new interpreter interface around it. Parchment, as it was named, was no longer a extension, but now a webpage that could run in any (modern) browser.
Dannii Willis started working on Parchment in late 2008. In early 2009 he decided to again separate Gnusto from Parchment, and moved its development to GitHub. In 2011 he started working on ifvms.js instead. Gnusto is no longer maintained.
Gnusto is licensed under the GNU GPL v2 license.
The latest Gnusto sources will be available at http://github.com/curiousdannii/gnusto/
Prior to GitHub, Gnusto has been developed at: http://www.mozdev.org/source/browse/gnusto/ http://hg.toolness.com/web-gnusto http://code.google.com/p/parchment/source/browse/trunk