"GanttProject is a cross-platform desktop tool for project scheduling and management. It is open source software under the GNU GPL V3 license".
To run it under OS/2-eCS you need to launch it with this command:
"java -Xmx512m -classpath "%CLASSPATH%;D:\<path>\eclipsito.jar" -ea org.bardsoftware.eclipsito.Boot ganttproject-eclipsito-config.xml -log %1 %2 %3 %4 %5 %6"
Or you can rename "ganttproject.bat" to "ganttproject.cmd" to run it.
Download Link: http://code.google.com/p/ganttproject/downloads/list (ganttproject-2.5.1-r1054.zip )
Official Project URL: http://www.ganttproject.biz/
