Open Source Hardware Is Not a New Concept

Hmmm, just because the schematics for something are available doesn't make it "Open Source". It needs a license which enables people to re-use, rebuild, share and potentially even compete with the original.

Just having the schematic available - but with no license - is more akin to "source available" than open source.

It's unclear what the license for the Air Gradient hardware is, as only the Terms & Conditions seem to mention anything related to usage, and it's piecemeal:

https://www.airgradient.com/terms-conditions/

Some of the points:

    * Reverse engineering allowed ;) Being open-hardware, we invite makers to extend our
    air quality monitors and explicitly allow additions on the hardware as well as the
    software.

    * Self-repair encouraged!

While that's better than typical closed source stuff, it doesn't sound like they'd be ok with someone wholesale reusing their design to launch a competing product.