Greenstone 3 was released yesterday. This version is a complete redesign and reimplementation of the current Greenstone digital library software (Greenstone 2), and is intended to increase the modularity, flexiblity, and extensibility of the application. Version 3 supports collections created in Version 2.
Warning from the website: "Please note, Greenstone 3 is our research version of Greenstone, and is still incomplete, and not stable. For a production digital library we recommend using Greenstone 2.")