Nightshade is a runtime environment for a Lisp programming language.
The goal of the Nightshade project is an entirely public domain system defined in a single language, which a single person can maintain fairly easily.
The system is most probably entirely in the public domain already. Most of the Authors have verified that they have given up ownership rights to the system.
Included in the system is an Emacs-like programmer's text editor, an interpreter, a byte compiler, a native compiler, a run-time program inspector, a profiler and higher-level libraries for tasks such as internet connection, mail handling and document processing. The primary human interface to the system is the editor, which has extensions for file management, reading mail and reading network news.
The Welcome node has some pointers for getting started in the editor.