The files more or less come from the WeBWorK Open Problem Library, and hence the license is the same.
Unless otherwise indicated, copyrights on the content contributed to this library are held by the author(s) of that content. This includes the problem files (*.pg) and any associated auxililary files such as images and custom macro files.
Unless otherwise indicated, all contributions are licensed under the Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. To view a copy of this license, visit
http://creativecommons.org/licenses/by-nc-sa/3.0/
or send a letter to Creative Commons, 444 Castro Street, Suite 900, Mountain View, California, 94041, USA.