  Aims. Optically thin plasmas may deviate from thermal equilibrium and thus,
electrons (and ions) are no longer described by the Maxwellian distribution.
Instead they can be described by $\kappa$-distributions. The free-free spectrum
and radiative losses depend on the temperature-averaged (over the electrons
distribution) and total Gaunt factors, respectively. Thus, there is a need to
calculate and make available these factors to be used by any software that
deals with plasma emission.
  Methods. We recalculated the free-free Gaunt factor for a wide range of
energies and frequencies using hypergeometric functions of complex arguments
and the Clenshaw recurrence formula technique combined with approximations
whenever the difference between the initial and final electron energies is
smaller than $10^{-10}$ in units of $z^2Ry$. We used double and quadruple
precisions. The temperature- averaged and total Gaunt factors calculations make
use of the Gauss-Laguerre integration with 128 nodes.
  Results. The temperature-averaged and total Gaunt factors depend on the
$\kappa$ parameter, which shows increasing deviations (with respect to the
results obtained with the use of the Maxwellian distribution) with decreasing
$\kappa$. Tables of these Gaunt factors are provided.

High Energy Astrophysical Phenomena