It started in the Dynamic Modeling group, part of MIT's Laboratory for Computer Science, today called the Computer Science and Artificial Intelligence Laboratory (CSAIL), in 1970.
While not in much use after the 1980s it had influence on other languages including Scheme and Common Lisp.
The Muddlers website works to preserve this particular part of the Lisp family tree by recording the history and information about the language while giving credit where due, develop an interpreter to run on modern systems that maintains the spirit of the initial implementation, and serve as a resource to help fellow muddlers.
The Muddle interpreter and documentation are free software, licensed under the GNU Affero General Public License, so that everyone will always have the right to study, share, and change them.