[detaro]

True, board layouts aren't either, forgot about that. The circuit itself can't be copyrighted, so you do not need a license to make your own board with the same components.

I personally quite like the approach of using the bootloader chip as light DRM: The majority of the value is in software you can freely use, with licenses provided. Prototyping with a Teensy and then making a product using the same parts and the libraries, not a problem. Just if you want to provide the same easy dev-board experience you need the bootloader chip (which you can buy and use for your own design) or invest your own development of an alternative.

[fermienrico]

Yep, I really like how the bootloader works - upgrades are drag and drop. I'll write to Paul if he is open for selling the bootloader license to me for commercial use. I am sure we can come to an agreement.

[detaro]

He sells the chip pre-programmed for the older versions: https://www.pjrc.com/store/ic_mkl02.html

Support for the chip used in Teensy 4 is apparently coming in the near-ish future: https://forum.pjrc.com/threads/57132-Bootloader-Chip-For-Tee...