Here is a geekier post about how to tweak Cura plugins and convert them to standalone Python scripts that post-process your g-code without Cura nor Skeinforge.
After I designed and used my wood gradient plugin, people naturally started to ask for the source code. I was a bit lazy first, because it was made for Cura 12.08: the patch I released was not very convenient, and Cura had evolved with a better and simpler plugin system, and included my own plugin.
Then, I got the time to fix it. Here is how I converted it to a standalone Python script that runs on its own, asking nothing to nobody.