It seems to use TL071 as a buffer amp; this wouldn't be anyone's first choice for a first-stage microphone amplifier, but for the advertised application of feeding into a smartphone or guitar amp its relatively high noise probably wouldn't bother anyone.
You could substitute that opamp for something considerably quieter, but it also depends on the resistor values around the amp. They didn't provide a schematic in the kit instructions so I'm not going to bother to figure that for them.
Also their comment about "motorboating" in the user manual probably means that the phantom supply isn't well filtered. This can cause problems with some microphones.