Why not? This language is being created while I progress on my research about language design and compiler engineering. This project grants me the freedom of independent research.
At this stage, one cannot compare sushi with other mature programming languages. I am still figuring it out the language’s purpose.
Definitely yes. Currently it lacks documentation. The only documentation available right now is the book. If you finish this book you can easily contribute to this project, but I am sure by end of this book you will have your own programming language. But if you still want to contribute, hit me up.