Electromagnetism Permeability of vacuum How vacuum could have electromagnetism Permeability when there is no molecule in it.
(Permeability  of other medium get describe with effect of their polar or magnetic molecule)
 A: One has to start with Magnetization, as it is a striking result of magnetism, and see how it is defined :

In classical electromagnetism, magnetization or magnetic polarization is the vector field that expresses the density of permanent or induced magnetic dipole moments in a magnetic material. The origin of the magnetic moments responsible for magnetization can be either microscopic electric currents resulting from the motion of electrons in atoms, or the spin of the electrons or the nuclei. Net magnetization results from the response of a material to an external magnetic field. Paramagnetic materials have a weak induced magnetization in a magnetic field, which disappears when the magnetic field is removed. Ferromagnetic and ferrimagnetic materials have strong magnetization in a magnetic field, and can be magnetized to have magnetization in the absence of an external field, becoming a permanent magnet.

This is how the dipole moments enter , by Magnetization.
Mathematically:
$B=μ_0H+M$ in SI units
If there are no dipoles  (vacuum)  there is no Magnetization, so B and  H are proportional , and  $μ_0$  is the vacuum permeability 
It is interesting to see the   plots relating B and H proportionality relative to vacuum:

If one wants to use $B=μH$ for materials , $μ$ defining the materials permeability, then one gets the confusion about dipoles. 
A: If $\mu_0$ was zero then there would be no magnetic field due to moving charges in the vacuum. $\epsilon_0$ and $\mu_0$ just determine the strengths of electric and magnetic fields in a vacuum, as $\epsilon$ and $\mu$ do in a dielectric. A medium isn't needed for permeability, or else magnetic fields would be zero in the vacuum in many cases. 
