I've printed two of these so far, one at 100% scale and the other at 48% and both bend perfectly well after gently but firmly breaking the initial stuck parts (which wasn't too hard, but be careful not to pinch your fingers). If the joints are truly fused together and you can't break it at all, chances are your printer isn't quite calibrated enough. I had this issue myself before I upgraded my belts and added tensioners to them. Once I did that I was able to print hinged parts without a problem. The spaces between the parts are small enough that even the slightest additional movement to the axes is enough to cause a hinge to end up fused. Tensioning the belts removed the extra movement my printer had when the belts were only hand-tightened.