Great plugin! I am developing a theme that I will sell on themeforest, and I want my users to have a popular posts widget. Yours is the best I have found, and normally, I would simply recommend the plugin in the documentation of the theme, but this time I need to change some of the code in your plugin's php file to match the design of the theme I am developing (they are deeper changes than the html options you provide at the bottom of the widget options (unfortunately)), so to use your plugin I need to edit the php files and include the plugin in my theme's final zip file. I realise that if you update your plugin and people who use my theme install the update, the plugin will break with my theme. But that is okay, I will update my theme every time you do that.
I just wanted to confirm that you give me permission to do this? I will of course leave all your credits at the top of the files intact. I will simply add a line at the top that says "Partly modified to work with X theme" so people know it's a slightly modified version of your plugin.
All the best.