blojsom is a full-featured, multi-user, multi-blog package written in Java. blojsom aims to retain simplicity in design while adding user flexibility in areas like back-end storage, flavors, templating, themes, and plugins.
I'm biased. A lead development steward of blojsom, but more importantly a user of blojsom for as long as the project has been active. As steward, I'm reactivating blojsom and leading a full on update of many of the libraries, the platform and the build infrastructure. Want to help? Connect with me on twitter @blojsomdev.