Lib Lib is a "media" server built on couchDB. "Media" is in quotes because the term is being used as loosely as possible (traditional digital items like books, music, video, as well as photos, digital artwork, event archives... really any digital "stuff" you want to keep).
This project is primarily a specification, however it also contains instructions on how to create your own and an initial implementation.
Because then you can do all kinds of neat "stuff" with it! When you store your digital stuff in liblib then it becomes a platform for anything you can think of. Check out the use cases