Seems an active community: "Last stable release": 2009.06.30 (http://en.wikipedia.org/wiki/Joomla)
Also in wikiped: a fork from Mambo:
"Joomla! is a free open source content management system for publishing content on the World Wide Web and intranets as well as a Model–view–controller (MVC) Web Application Development framework. The system includes features such as page caching to improve performance, RSS feeds, printable versions of pages, news flashes, blogs, polls, website searching, and language internationalization. Joomla is licensed under the GPL, and is the result of a fork of Mambo.
"It is written in the PHP programming language and uses the MySQL database system to store information."
I have a Wordpress that I have been using for my business and it just seems stodgy compared with Joomla. Wordpress seems to be stuck at blog, where as Joomla seems to be much more flexible.
That said, I am still experimenting and this new project needs to support multiple users in a controllable way.