How can an online library, with digital copies of a book, only have so many books to “loan” out?
In: 4
Because of licensing. The digital copies are limited in number so that they can be checked out as if from a physical library, but not endlessly duplicated. Otherwise how would the author or publisher of the book ever make any money selling books?
Because those are the terms the publisher made them agree to when they bought their copies.
Just because something is physically possible doesn’t make it legal.