I cannot find a statement of licensing terms anywhere in the Ethernet library code, except "all rights reserved" in w5100.c .
I would like to use this code, and to modify it, and publish modifications.
Would the author(s) please clarify their copyright and terms of license, preferably with a header on each file?
The C code under the utility/ directory is only slightly modified from manufacturer's app note "W5100 Driver Source". I've posted a note on their developer's Q&A page asking for license clarification.
WizNet has responded to my inquiry:
Yes, it is free.
You can get not only driver code but also any other materials from our >web site.
Written by Adam Tilghman.
Are we permitted to incorporate "W5100 Driver Source" into our
products without paying an additional license fee? May we distribute
the source code to our customers for their reference? Thank you.
Given that we're discussing vendor-supplied source code which enables use of their embedded product, I'm satisfied with the response and wouldn't hesitate to redistribute their code.
Of course your lawyers may advise you differently