First of all, if you do not obtain the author’s consent, use it for commercial purposes. That would be illegal if the author of the book pursues it.
However, there is no need to be so serious about this thing. As long as you are not using it for business and for profit. And if the scope of dissemination is not very large, generally the author will not know about it or will not pay attention to it at all, and it will be fine.
This is like everyone knowing that using pirated software is illegal or immoral. However, there are a lot of pirated software or activation tools circulating on the Internet. No one cares about it. How many people are using it? . .