Some people have criticized that digital libraries are hampered by copyright law, because works cannot be shared over different periods of time in the manner of a traditional library. The content is, in many cases, public domain or self-generated content only. Some digital libraries, such as Project Gutenberg, work to digitize out-of-copyright works and make them freely available to the public.
See List of digital library projects for an extensive listing.
The Digital Library is:
While the first definition is focussed on ebooks, this is much more general. Information objects can be anything expressed in a digital format: books, journal articles, maps, picture, sounds, etc. The important thing is that, like a "regular" library, the Digital Library is organised to store and make accessible the objects it contains, but the storage and retrieval methodologies used differ in being "electronic".