This work (the program source code) is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. See http://creativecommons.org/licenses/by-nc-sa/3.0/ for full license.
The images generated by this code are licensed under a Creative Commons Attribution 3.0 Unported License. See http://creativecommons.org/licenses/by/3.0/ for full license.
For both licenses, providing a link to http://regexper.com/ is considered sufficient for attribution.