The source files mention the BSD license, but they don't say which version of the BSD license; there are 3 different BSD licenses:
2 clause BSD license
3 clause BSD license ("New BSD", with endorsement clause, used in this PR)
4 clause BSD license ("Original BSD", with marketing clause)
The 4 clause BSD license is the most restrictive, and it's considered problematic, because it requires mentioning the University of California, Berkeley in all marketing.
The 3 clause license is the most commonly used, and the only addition compared to the 2 clause license is that using Adafruit's or other authors' names for endorsement/promotion of derived software is not allowed without written permission (probably a good idea, even if Adafruit's trademark probably already prevents this).
A LICENSE file is pretty common practice, and it's the first place where most people look for the license. It's also important to include the full text of the license somewhere, since now it's unclear which BSD license the source files refer to.
I'd suggest adding a LICENSE file to all Adafruit libraries.
Add a LICENSE file and mention it in all source files. License text is generated with this tool: https://soulsphere.org/hacks/bsd/
The source files mention the BSD license, but they don't say which version of the BSD license; there are 3 different BSD licenses:
The 4 clause BSD license is the most restrictive, and it's considered problematic, because it requires mentioning the University of California, Berkeley in all marketing.
The 3 clause license is the most commonly used, and the only addition compared to the 2 clause license is that using Adafruit's or other authors' names for endorsement/promotion of derived software is not allowed without written permission (probably a good idea, even if Adafruit's trademark probably already prevents this).
A LICENSE file is pretty common practice, and it's the first place where most people look for the license. It's also important to include the full text of the license somewhere, since now it's unclear which BSD license the source files refer to.
I'd suggest adding a LICENSE file to all Adafruit libraries.