Final answer:
A book published in 1894 can be used legally without permission or fee due to the concept of public domain.
Step-by-step explanation:
The legal concept that allows a book published in 1894 to be used legally without permission or fee is public domain.
When a work enters the public domain, it means that the copyright on the work has expired, allowing anyone to use, copy, distribute, or modify it without infringing on copyright laws.
In the case of the book published in 1894, since it is now in the public domain, it can be used freely without the need for permission or payment.