You can upload Gerbers/ODB++ if you like. We also sign custom NDA's. We count many of the worlds largest corporations as customers so this is pretty standard.
In order to receive a quote on CircuitHub, you will need to upload the original design files from your EDA tool, or an export that carries the same data. This allows us to provide instant quotes and automate the manufacturing process to lower lead times and cost. Currently, our platform works with Altium, KiCad and Fusion 360 files, and with ODB++ and IPC-2581 exports from any design tool, including Cadence Allegro and OrCAD.
We do not accept Gerber files on their own because they do not contain all of the design and assembly data required by our automated process. We do use your Gerber files when you upload them together with an ODB++ or IPC-2581 export, or with Fusion 360's EAGLE exports, which describe the parts.
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Other vendors don't require this. They just need the gerbers, BOM, and CPL files. That's way different than source files or ODB++/IPC-2581 exports, which is basically the same thing as source.
Would you address other concerns voiced above? They are pretty serious points or allegations. Also, a PCB sourcing should not require a custom NDA when the selling point is convenience, legal protection, and speed vis-a-vis overseas sourcing.
I second the use of NDA/privacy gaurantee as default. It shouldn't be opt-in with friction. Of course if I want to use a custom/overriding NDA then i'm happy to contact you to review.