License for Commercial Plugin

I am creating a plugin for Blender. It’s a paid plugin. The plugin works via a script that you install through User Preferences > install from file function. Bundled with the plugin is also a Blender file and a link to an external library. How would I go about licensing this plugin to prevent people from ripping off my work and re-selling it themselves?

I’m pretty sure if you are importing BPY into your script, it counts as a derivative of GPL code, and thus MUST be GPL. You have to provide your source on request to anyone who purchases your product. What they do with it after you provide it to them is beyond your control.

thank you!

Yap, you can’t license it in a way that makes it incompatible with the GPL and one of the key compatibility rule is that people that legally acquire the code - by buying it from the original author, if it is for sale - can resell it. Basically after the first paying customer it’s free beer for everyone, unless he decides not to share the code with his friends.
Nonetheless, for a very interesting mix of social behavior and cultural conditioning, if you sell it, most people that want it will also buy it.