It should be compatible with the 64-bit puppies - it has always worked for me on Lighthouse64 without any problems. You just need to extract the file into your "/opt" folder, the go into the programs "bin" directory and run Gimp Painter from there.
Important point of note - do NOT delete your vanilla Gimp 2.8, as it depends on it.
Running this will not affect your vanilla Gimp 2.8 installation, and you will still be able to run it seperately if you need to.
More knowledgeable linux users will know how to make a .pet and .sfs out of this.
I have no association to this project, so I don't know about the status of the 32-bit version.