Interesting circuit.
I've tried a similar thing before but found it difficult to get the maximum noise output which is reached, just above the minimum current required to turn the reverse biased transistor on, so it operates in the avalanche region. This circuit achieves this by putting Q2 in the feedback loop of Q1 and AC coupling its emitter to 0V. As soon as Q2 starts to breakdown, Q1 turns on a bit, diverting the current round it, so it balances itself with a tiny current through Q2.
Yes, you need to AC couple the circuit to the amplifier, in order for it to work. The DC voltage on Q1's collector will be around 6.6V (Q2's breakdown, plus VBE of Q1). Say you need a gain of 5. Without AC coupling, the amplifier will try to drive its output to 6.6*5 = 33V, plus the noise signal, which will be out side the power supply voltage range. If the DC is blocked by a capacitor, then it will just amplify the AC noise signal, not the 6.6VDC bias.