In order to download the source code for my experiments you have two options.
1) If the code is included in the experiments description just double click it. Double clicking will highlight the code. Then you can just copy and paste it into the Arduino IDE.
2) Download the collected code from Github. I have setup a Github repository for my experiments. There you can browse all source files. You can download them from there seperately or all together in one single zip file.
With regard to what you can do with this software – everything is open source. To be more specific I have put the code under the GNU General Public License V3. So this is not public domain. In case you need a more permissive or a commercial license feel free to contact me.