Hey there - the source for Mimic 3 can be found here: https://github.com/mycroftAI/mimic3 It can run CPU only or accelerated with a GPU.

Regarding the BOM, I assume you mean the Mark II? That you can find here: https://github.com/MycroftAI/hardware-mycroft-mark-II/tree/m... We actually ended up designing our own RPi daughterboard called the SJ201. It's mostly an audio front end with an XMOS XVF-3510 and dual mics, but also includes a 23W amp, some LEDs for feedback, buttons, a hardware mic switch, GPIO breakout and power management (amongst other things).