Hi there, it's been awhile since I've posted on the forum. Just to say that the synth is truly open source now. I mean, it was already, but if you want to build it, to know what to buy, to order the pcb, to get the arduino code, and to read the soldering manual, everything is here : https://www.s8jfou.com/synth
I'm sorry I know I'm a bit late and many people asked for that. The only reason I did not share these documents is my lazyness. I took the picture for make the soldering pdf in 2021, and I just made the thing in photoshop last month. (the synths was born in december 2019 by the way...)
I'm pretty sure nobody will never build it but in case of, it's now much more easier. Cheers 
Billy.