3D printed part sticking to the support layer
I finally found out two causes:


The 3D printer has default settings for ABS, and since there is no printer bed settings in ReplicatorG, the bed temperature was set to 110&nbsp;°C instead of &nbsp;60°C. I fixed the setting directly on the printer itself.
It seems that one side of the printer bed was little closer to the nozzle than other sides (relatively to the extruder) and this added a pressure on the support layer. I found this by observing the structure of the support layer that was little more compressed in one side. That was easy to fix by iteratively tightening/loosening the screw of that side and observing the support layer (and canceling the print if it is not homogeneous).


I installed Ultimaker Cura and Slic3r to try them and I found that Ultimaker Cura was not adapted to my printer (I did not found a complying model), Slic3r seems to be okay but I was not able to fit my big part inside of it.
I am trying to use the maximum available space for my part, perhaps I need to change some settings for Slic3r and anyway it is already working on ReplicatorG.