The GIMP can be run on most major platforms. For instructions on how to obtain and install The GIMP download page
Now Download the Platonic Solids Foldables Plugin
by clicking on gimp_foldables_scripts.zip. Then unzip the files into your GIMP scripts folder. From The GIMP documentation: Installing Script-Fus
You will also need to install the Kaleidoscope plugin for GIMP. Hopefully you are running Linux and can follow the instructions here
to install the Kaleidoscope plugin. Otherwise acquire some other software in your chosen OS that will allow you to create kaleidoscoped images.