I had a quick look at some of the Arduino projects, and found most of them stating "This example code is in the public domain.", event those modified by (as I guess) participants of the coder dojos.
Of course, all modifications are copyrighted by the participants, so they are either "All rights reserved" or need to be placed under an express licence (which the minors can only do with parental consent).
The public domain claims in the source files, however, are most likely wrong and illegal.