The description is at http://rollerweblogger.org/project/page/about:
Roller is the open source blog server that drives Sun Microsystem's blogs.sun.com employee blogging site, IBM DeveloperWorks blogs, thousands of internal blogs at IBM Blog Central, the Javalobby's 10,000 user strong JRoller Java community site, and hundreds of other blogs world-wide. If you want to set up a blog server for yourself or for several thousand of your closest friends, then Roller is the perfect choice.
The Roller project is in the process of moving to the Apache Software Foundation (ASF) and is currently part of the Apache Incubator program. The ASF incubation process is designed to ensure that projects entering Apache have a strong and diverse community, have Apache compatible licensing and work according to the ASF's philosophy and guidelines for collaborative development.
Lotus Connections (IBM product)
Lotus Connections is more the just a blog, and is positioned as "social software". At http://www-142.ibm.com/software/sw-lotus/products/product3.nsf/wdocs/lcintro:
Lotus Connections has five components that work together: Profiles, Communities, Blogs, Dogear and Activities.
Lotus Connections blog product page, at http://www-142.ibm.com/software/sw-lotus/products/product3.nsf/wdocs/lcblogs:
Because blogging is as natural as writing an email to a group, one can shre his thoughts and solicit feedback without worrying about filling up everyone’s inbox.
Blogs help you communicate with your peers or colleagues and nourish innovation.