For the recent project I had to prepare, I did have to generate a
GANTT chart.  I tried using TJ2 via org but found the current
implementation not suitable for my way of working.  Instead of using
TJ, either 2 or 3, I simply created my own chart using tikz in latex.
To make my life easier, I created a number of latex commands for this.

I've now developed some code which will take an org table and create a
GANTT chart.  Some of you may find this useful so I've attached an org
document with all the codes (emacs lisp + latex) along with an
example.  I've also attached a PDF so you can see what I get.

The codes are not necessarily easily customisable so they may not do
what you want.  For the types of project proposals I have to prepare,
the level of detail I have here is sufficient.

eric