  We study the Drude weight $D(T)$ at finite temperatures $T$ of an integrable
bosonic model where the particles interact via nearest-neighbour coupling on a
chain. At low temperatures, $D(T)$ is shown to be universal in the sense that
this region is equivalently described by a Gaussian model. This low-temperature
limit is also relevant for the integrable one-dimensional Bose gas. We then use
the thermodynamic Bethe ansatz to confirm the low-temperature result, to obtain
the high temperature limit of $D(T)$ and to calculate $D(T)$ numerically.
