Today Imtiyaz and I did a small hack in the Flex charting code and removed the Trial message from the Charting component by writing 1 simple actionscript lines.
what you need to do is in the creationcomplete of any charting component write the following code
// var arra : Array = new Array();
// for(var i:int =0;i<this.numChildren;i++){
// arra.push(this.getChildAt(i));
// }
// the above 4 lines are just to check what r the childs added
(this.getChildAt(this.numChildren-1) as TextField).htmlText = ” “;
we tried to set visible false but that dint work we also tried to remove the textfield child alltogether but that too dint work 
but finally it was the html text property of the textfield that gave way 
now you can also add your custom trial message to your application 
just replace the blank with your text for example:
(this.getChildAt(this.numChildren-1) as TextField).htmlText = ” YOUR MESSAGE”;
But its better that you buy your own licence key for charting. The above example was basically for educational purpose. have fun
