Well I was interested up until the point I heard about the license key and checking back to the server.....I had a theme that tried to do that which really ticked me off. I'm just one of those 'weird' guys who refuses to run any script with encrypted code or callbacks built in.

When I run into that, the first order of business is always to decrypt everything, remove all callbacks and then determine if the code is solid enough for my use. --Lesson was learned from the theme that was encrypted when I purchased it. The dev's were positive that it was secure, and only after 'opening' the code up did I find tons of css injection points and function vunerabilities. (No it was not a warez theme, but one I purchased directly).

I'm not saying that your code is bad, haven't purchased it, I'm just making a point against your 'model' is all. It does nothing for protecting your plugin, it just causes me extra headaches by having to spend the time to decrypt and null it is all...