Sonar is an open source project hosted at Codehaus. Download and install your own copy.
Version: 3.0.1 (May 14, 2012), License: LGPL.

All in one
Sonar is an open platform to manage code quality. As such, it covers the 7 axes of code quality:
Extend with plugins
Covering new languages, adding rules engines, computing advanced metrics can be done through a powerful extension mechanism. More than 50 plugins are already available.
Languages covered
Java is built in. Open Source and commercial plugins enable to cover C, C#, Flex, Natural, PHP, PL/SQL, Cobol and Visual Basic 6.
 
In 3 clicks
Sonar has got a very efficient way of navigating, a balance between high-level view, dashboard, TimeMachine and defect hunting tools. This enables to quickly uncover projects and / or components that are in Technical Debt to establish action plans.
Quality is central
Sonar is a web-based application. Rules, alerts, thresholds, exclusions, settings… can be configured online. By leveraging its database, Sonar not only allows to combine metrics altogether but also to mix them with historical measures.