It’s Open Source under the GNU General Public License. This means that you can do anything you like with the code but, if you distribute copies (even compiled copies burned on to chips) you must also distribute the source code with it. Including your modifications.
If you want it with a different license, contact me.
The code compiles and runs fine with Cygwin make. It would take some skill to get it to compile under a different environment such as the Arduino IDE.
I’ll try to explain what’s going on in the code in later postings. For now, Click Here to download.