SpagoBI code base is stable and well-commented, but it received little popular attention. The absence of books as well as the lack of case studies by third parties are among the possible causes for that.
Tagged: OW2 Toggle Comment Threads | Keyboard Shortcuts
Open source projects are planned, developed and maintained often using accessible Revision Control systems (e.g. Bazaar, CVS, Git, Mercurial or SVN), Collaboration (blogs, forums, IRC channels, mailing-lists and wikis) and Tracking Systems (e.g. bugzilla, GNATS, OTRS, trac). Despite going through them all can be time-consuming, those are the primary source of information to know more about an open source project.