public class IntelliGanttWebPartInstance : WebPart
protected override void CreateChildControls()
That's it. The only difference between the IntelliGantt Web Part in sandbox mode and the 'normal' IntelliGantt Web Part is the latter is able to plug into the web part editor forms to make it easy to configure all the IntelliGantt Web Part options. In sandbox mode, you'll have to supply all the options yourself in the 'Custom Initialization Parameters' field.
However, we realize that sometimes policy will dicate that the IntelliGantt Web Part is deployed to the SharePoint 2010 sandbox. Here's how to do it.