Where's the BOM? Specifically, the motor? 

The GITHUB documentation MENTIONS the BOM, but does not provide it. I'm interested in finding out how to obtain the motor, and then I can either try to install myself or, as the notes suggest, go to a bike shop to help in the installation.

I can do the 3D printing of the battery mounts and also the wiring.

Assuming I can get the project working I could add power monitoring/logging to measure performance and maybe crowdsource results with other makers.

Charlie in Houston, TX

SOME answers to my own question (google search on "mid-drive bike motors" : 

BAFANG Electric Bicycle Conversion Kit ($899)
https://www.amazon.com/Bafang-Lastest-Electric-Bicycle-Conversion/dp/B01FX7GL1Q

And

Luna Cycles Kits
https://lunacycle.com/mid-drive-kits/

BEST answer so far, article at ELECTRICBIKE.COM

26 Mid Drive Kits for DIY Electric Bikes
https://www.electricbike.com/mid-drive-kits/

Looks like an awesome project! Out of curiosity, what is the max speed the bike can reach and for how long? Keep up the great work!

A very nice project. I just wish batteries here in Sweden were cheap enough to utilize this way. Had a look online and 2 of those batteries would cost roughly 3600sek which is in the same region as a cheap e-bike battery of >10Ah.
What happens when 2 batteries are inserted if they have uneven charge/voltage? Does the internal BMS:es even the voltages out safely, or is there an unsafe "fast charge" of the battery with lower voltage?