Is it possible to use custom task appearance (as indicated in Custom Appearance sample application) or task bar templating (as indicated in Bar Templating sample application) within the Gantt Chart control from Gantt Chart Library for WPF or Project Management Library for WPF data binding it to a collection of custom task item data objects that do not inherit from DependencyObject (and therefore don't support WPF attached properties)?
Regarding custom appearance (task bar colors): As you cannot set the attached property GanttChartView.StandardBarFill (of type Brush) values to the custom task data items bound to the control (or SummaryBarFill, MilestoneBarFill for other types of tasks), you could still specify attached property values directly to the managed Task objects, generated by the internal (or customly defined) TaskManager. To obtain a reference to a managed Task object from the Gantt Chart control, use the provided indexer, or one of the GetTask or GetTaskAt methods.
Regarding bar templating: Your custom task item data objects may define custom properties (for example, MyValue) that you can then access directly from within the bar template of the task:
Notice the Item. prefix of the MyValue property, that actually reaches your custom task item data object from the managed object level that the template refers to by default.