> one vendor's kit I did look at explicitly stated their boards were not licensed for that kind of commercial use. Qualcomm could very well make their boards for development, test, and evaluation purposes only.
Under what legal theory?
As far as I can tell, if they even attempted that, all they could do is deny any kind of warranty claims from you and try and stop distributors selling you any more of their brand parts.
One way they could do this is grant you a patent license only for some kinds of use.
(and eg. make sure their products are useless without some patent license for some software driver or algorithm)
They could claim copyright infringement if you distribute their SDK in your firmware without their permission.
The "we have lawyers and lots of money to enforce things that are on shaky legal ground and you will likely settle instead of fighting in court" legal theory, I presume.