It's Official, Microsoft Likes Open Source Web Content Management
CMSWire
At the announcement event, Joomla! leader Ryan Ozimek talked about Joomla!'s support saying, "WebMatrix puts the power and user-friendliness of Joomla! ...

Microsoft Releases WebMatrix Web Publishing Tool
PC Magazine
... Joomla, Drupal, and Umbraco. The key feature is that WebMatrix houses the Web server, database, and programming framework in one organized space. ...