Evergreen, highly scalable library software with GPL

This is the project site for Evergreen, highly-scalable software for libraries that helps library patrons find library materials, and helps libraries manage, catalog, and circulate those materials, no matter how large or complex the libraries. The software, also called Evergreen, is used by libraries to provide their public catalog interface as well as to manage back-of-house operations such as circulation (checkouts and checkins), acquisition of library materials, and (particularly in the case of Evergreen) sharing resources among groups of libraries. The Evergreen Project was initiated by the Georgia Public Library System in 2006 to serve their need for a scalable catalog shared by (as of now) more than 275 public libraries in the state of Georgia.

Source: evergreen-ils.org