  We explore a number of explicit response formulae around the boundary driven
zero range process to changes in the exit and entrance rates. In such a
nonequilibrium regime kinetic (and not only thermodynamic) aspects make a
difference in the response. Apart from a number of formal approaches, we
illustrate a general decomposition of the linear response into entropic and
frenetic contributions, the latter being realized from changes in the dynamical
activity at the boundaries. In particular, in this way one obtains nonlinear
modifications to the Green-Kubo relation. We end by bringing some general
remarks about the situation where that nonequilibrium response remains given by
the (equilibrium) Kubo formula such as for the density profile in the boundary
driven Lorentz gas.
