This is what worked for me...(tried in Windows platform few months ago)
a) Go to folder "...\GenOpt\example\energyplus", copy folder 7_0_0 and paste in the same directory and rename it to 8_3_0.
b) The go inside ....\example\energyplus\8_3_0\GPSHookeJeeves and edit optWin7.ini with text editor
c) in optWin7.ini update configuration File 1 to EnergyPlus-8-3-0-Win7.cfg";
d) Go to folder ...\GenOpt\cfg and copy and paste in the same directory EnergyPlus-7-0-0-Win7 and rename it to EnergyPlus-8-3-0-Win7.
e) Change the address of RunEPlus.bat, thsi is what I have C:\\EnergyPlusV8-3-0\\RunEPlus.bat\
f) Then if you double click on genopt.jar and then in File-->Start select optWin7.ini you edited in point c) above, GenOpt should run.