Maybe I'm not reading correctly, but it seems the project is about making a language compiler and not a language itself?
> You can build an interpreter or a compiler, so long as it can run or build examples of code in the programming language you create.
No you create a language, but it needs to be able to run. So need to either build a compiler or interpreter to make the language do things.
Designing a language is more about defining a specification. Then 10 different compiler engineers may pick that spec up and implement 10 different implementations of the same language, for example.