Taskjuggler
From TaskArtist Wiki
Taskjuggler III is the solid core TaskArtist is based on. It schedules the projects and creates output files (reports). However, it is command line only. That is where TaskArtist comes into play. TaskArtist provides a comfortable cocoa based user interface on top of taskjuggler III.
The official website of taskjuggler is located at: http://www.taskjuggler.org/
You may also like to discuss syntax or report related topics with other taskjuggler users from all around the world using the Taskjuggler User Group.
There is also a group for reporting taskjuggler related bugs, the TaskJuggler Bugs Group.