As we’ve discussed at great length, the Internet Archive’s Open Library system is indistinguishable from the economics of how a regular library works. The Archive either purchases physical books or has them donated (just like a physical library). It then lends them out on a one-to-one basis (leaving aside a brief moment where it took down that barrier when basically all libraries were shut down due to pandemic lockdowns), such that when someone “borrows” a digital copy of a book, no one else can borrow that same copy.