eduke32 doesn't seem to have an option for output sound over hdmi.

For rtcw, you could redirect the oss as:
echo 'wolfsp.x86 0 0 direct' > /proc/asound/card0/pcm0p/oss
(this didn't output to hdmi though but allowed the sound to work)

Taking a stab in the dark I tried:
echo 'eduke32 0 0 direct' > /proc/asound/card1/pcm3p/oss
echo 'eduke32 0 0 direct' > /dev/snd/pcmC1D3p

Neither of these worked.

Does anyone know how to do this, or at least redirect it?