What is the license of Diigo Firefox extension?

Well, I don't think you will be pleased with my idea. If it's not open-sourced, I will just create proxy that will intercept all external connections of your extension and redirect them to my own server. I'm really concerned about exposing my data to thid-party... Of cource, it would be easier to just add server selection into extension iself, but if you don't want this functionality - it's your right...