Overview
RETRO is a small Forth, modeled after cmForth, colorForth, eForth, and Pygmy. It uses some, but not all of Chuck Moore's newer ideas. It's clean, elegant, and tiny. It doesn't have many features, and isn't particularly useful by itself, but it's easy to grasp and easily adapted to various uses.
RETRO runs on a lightweight virtual machine called Ngaro. This emulates a MISC-style instruction set, allowing RETRO to be written in a simple machine forth language. This machine forth is written in Toka.
RetroForth is released into the public domain. In short, this means that it can be used, modified, or redistributed without restrictions.
For support, try the new mailing list, message board, or visit the #retro channel on irc.freenode.net.
Download
RETRO is now packaged with Ngaro and Toka and some scripts to allow easy building and running. This should hopefully make things a little easier for those wanting to try it out.
The current release of RETRO is 2008.04.13
Past releases of RetroForth can be found in the archive. Most of the old versions are located there, but a few have been lost through the years.