We have a four-gluon vertex and a gluon vacuum condensate. Why doesn't this provide us with gluon masses, as in the NJL model where the condensate gives rise to an effective mass term?
Well, in the NJL model you get rid of the gluon. They are considered to be frozen in the low energy limit where you are working because the mass is higher than the energy. Thus you are only working with quarks, and you consider interaction between quarks via effective coupling constants.
But in the standard model, gluons (seem to) acquire an effective mass because of confinement. That's why the range of the strong interaction is short. If you compare with photons, they have no electric charge and the range of the electromagnetic force is infinite.