[http://www.activestate.com/Products/komodo_ide/ Komodo IDE] from ActiveState is a rich ["IDE"] for Perl, Python, PHP, Ruby, JavaScript, XML, HTML and Tcl. It offers many integrated tools (i.e. code completion, code debugger, regular expressions toolkit, etc).
ActiveState also introduced an open-source, free Komodo-based editor, called [http://www.activestate.com/Products/komodo_edit/ Komodo Edit], which is less functional but available at no cost.
The source code is available from [http://www.openkomodo.com/ Open Komodo] and is distributed under the Mozilla Public License. The source code to build Komodo Edit is available [http://grok.openkomodo.com/source/xref/openkomodo/trunk/ here.]
The page titled "IntegratedDevelopmentEnvironments" includes several reviews of Komodo. [http://www.unixreview.com/documents/s=10125/ur0704b/ Here], in April 2007, is one of Komodo 4.