What is the word for freeware functional clone of sh, with parts of ksh, bash and full POSIX compliance

The word you are looking for is "dash". Dash is a Unix shell that is a freeware functional clone of sh, with parts of ksh and bash, and full POSIX compliance. It is commonly used as the default system shell on Debian and its derivatives, including Ubuntu. Dash is designed to be a lightweight and fast shell, making it ideal for use in resource-constrained environments.