...hm... the sourcecode shows only delays, no pitch shift per "voice", this can't work (obviously, as you can hear)
What ever this effect is, it's not a chorus :-( Perhaps the same can be done with the delay-effect.
Looking over the source, yeah, that looks like a set of static comb filters. Something like the multi-tap delay line followed by a mixer.
Take a look at the Flanger class. It has sinusoid modulation and interpolation. Flange with slow modulation and overall delay of 25-ish milliseconds moves into chorus territory.
When I wrote the chorus and flange effects, I used this as a guide: http://www.cs.cf.ac.uk/Dave/CM0268/PDF/10_CM0268_Audio_FX.pdf
It says that chorus doesn't use modulation so I didn't try any. I couldn't find anything else which explained how to get those effects.
evidently a lfo modulates a clock signal, giving variable delay times. From the page ....
"The chorus effect is created by the slow modulation of the delay time using a Low Frequency Oscillator (LFO). As the LFO cycles, the delay time goes up and down and therefore the delayed audio pitch slightly shifts up and down."
Sounds a bit like how imagined a flanger would work ....
the delay is a bucket brigade device (whatever the hell that is)