On a sidenote: In a community such as this where we are all trying to improve for each other, I don't understand why someone would release closed code. But that's just me.
I would follow up with Bossland, Hawker, or Tony before doing anything like this my friend. By making this closed source, your removing the help that the community (Developers atleast) can provide you and your users of the plugin. Think about it before making a final decision.