Math Minion is:

Free

Math Minion is free software: you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

The source code is available on GitHub.

Math Minion is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

Private

Math Minion is written in javascript as runs completely inside your web browser. No calculations are performed on the server and no information sent to it beyond what the browser needs to send to load a static web page.