Abstract: Neutron stars, particularly during and after mergers, are driven out of chemical equilibrium. Capturing the role of dissipative effects in their gravitational wave emission is both essential for building accurate models and a powerful probe of matter at extreme densities. In this talk, I present progress within the BDNK hydrodynamics framework, which offers a causal, stable first order theory for studying out of equilibrium dynamics. I will examine how viscosity influences the GWs emitted during neutron star mergers and how we can model these effects. I will then share recent results on scattering of GWs by viscous stars, including superradiant phenomena. Finally, I outline ongoing work on radial stability and oscillation frequencies of viscous stars.