The gantt you pointed does support drag and drop of tasks only within the same row, in the same way as our gantt widget: http://www.tgantt.com/treegrid/www/Gantt.html#..*ExamplesGantt*Html*Gantt*Gantt.html Let me know if I am missing something.
You can check on here : http://www.treegrid.com/ . There has a gantt chart and most of the functionality that I want is there.
Drag and drop of tasks within the same row is supported, and you can test it here: http://demos.telerik.com/kendo-ui/gantt/index Reorganizing tasks outside of their row is not supported by gantt definition, because this would require to reorder items in the left-side treelist section. Do you know of other javascript gantts which support the latter?
One task may have sub task that kendo already have but kendo should allow drag and drop each other between that line or out of the line.