I’m sorry walter it’s another typo in my initial question. The “right” is the “from” and the “left” is the “to”. You can see the arrow in the first image. In fact when I start to drag the link the direction is correct, but when the nodes are linked the port seem to be on the bad direction :
The layered Layouts, such as TreeLayout and LayeredDigraphLayout, by default set the Link.fromSpot and Link.toSpot of each Link to match the general direction that the layout is going. So in your case, where TreeLayout.angle == 90, Link.fromSpot will be set to go.Spot.Bottom and Link.toSpot will be set to go.Spot.Top.
For most apps, that works well, but it appears that your nodes do not have their ports at the top and at the bottom of the node. So you can tell the TreeLayout not to set the spot properties on the Links by setting two properties on the TreeLayout: