I added JGoBasicNode objects to a JGoArea, but when I resize the JGoAreaObject, the nodes inside it resizes as well, and their shapes are corrupted.
How can I resize the area independantly?

You can’t resize a JGoArea by itself, since by itself it does not have any independent bounding rectangle. By definition the bounding rectangle of a JGoArea is just the union of the bounding rectangles of its child objects.
Maybe you just mean to JGoObject.setAutoRescale(false).
But if you do that for all of the children of a JGoArea, trying to resize the whole JGoArea won’t change anything.