Wikipedia
TaskJuggler is GPL-licensed ( free software) project management software that runs under the Linux and Unix operating systems and is programmed in C++ using the Qt toolkit and KDE libraries. The TaskJuggler Project was started in 2001 by Chris Schläger. Early releases provided a command line tool that generated HTML reports. From August 2005 to July 2010, the package also provided a graphical user interface based on the KDE libraries.
TaskJuggler III was released on 5 July 2010. It is a completely re-implemented version of the TaskJuggler 2.x series and written in Ruby. The graphical user interface from the 2.x version has not yet been ported to TaskJuggler III; TaskJuggler III documents, which are plain text files, are edited with a text editor and processed on the command line.