MuJS is a lightweight implementation of the Javascript language in a library. MuJS is licensed under ISC license which is FSF approved and compatible with GPL. MuJS rust bindings are licensed under GPLv3.
Its primary purpose and design is for embedding in other software to add scripting capability to those programs, but it can also be used as an extensible scripting language.
In contrast to other programs that are large and complex, MuJS was designed with a focus on small size, correctness and simplicity. MuJS is written in portable C and implements ECMAScript as specified by ECMA-262.
The interface for binding with native code is designed to be as simple as possible to use, and is similar to Lua.
For more indepth information about MuJS see MuJS Reference Manual.