question is a bit old, but as i just had the same problem. the answer is simple. gasp supports methods and properties. it will automatically determine what to use:
To manipulate a kineticjs object just tell it what setter to use, and don't forget to draw the object. you could use the onUpdate callback for that:
TweenLite.to(obj, 2 { setX : 300
onUpdate : function () {
obj.getLayer().draw(); }})