Open-source means I have the license to use it in ways that are defined in an agreement outlined in the specific open source license (say MIT license). Paul provides a bunch of stuff for their users, but I cannot copy his designs and bootloader (which is closed) in a commercial project without taking on liability.

The problem is a philosophical one as well - Half-open or "visible source" projects exploit benefits of the open-source community (engagement, contributions, feedback, etc.) without giving anything back to the community (license to reproduce freely). I have a problem with this. Either make something completely closed source (totally fine) or make it completely open source. Another example is Numworks calculator ("visible source" under CC license, wtf is wrong with these people) : https://github.com/numworks/epsilon/issues/38

The Numworks guys are just getting free labor which is all the enthusiasts working on the code without paying anything back to the community! Completely abhorrent behavior and should be exposed.