I think you are confusing two books. The author has a book on SSH tunneling and a lab guide for an interactive lab they offer about SSH tunneling.

The first is free, the second is a commercial product.

I am not selling anything and the author of this book is giving it away for free. The lab guide and access to the lab servers cost something.

OP, for what it's worth, this is a great resource regardless of license nitpicking. Thanks for publishing this repo.