How to convert Jmodelica-Optimica code to openmodelica-Optimica code

Question

this code is from Akesson et al., Modelica Conference 2009 paper.

package y

//A Modelica model of a van Der Pol oscillator.
model VDP
Real x1(start=0);
Real x2(start=1);
input Real u;
equation
der(x1) = (1-x2^2)*x1 - x2 + u;
der(x2) = x1;
end VDP;

//An Optimica optimization specification based on the van Der Pol Oscillator.
optimization VDP_Opt(objective=cost(finalTime),startTime=0,finalTime(free=true,initialGuess=1))
VDP vdp(u(free=true,initialGuess=0.0));
Real cost (start=0);
equation
der(cost) = 1;
constraint
vdp.x1(finalTime) = 0;
vdp.x2(finalTime) = 0;
vdp.u >= -1;
vdp.u <= 1;
end VDP_Opt;

end y;

How to make this code work on Openmodelica-Optimica?