Paid theme

Hello..

I have a theme hosted in WordPress Theme Directory. Of course it is free to use & download.

But I just want to know is it allowed for me to create a paid version of my theme which offers more features? The paid version will be released under GPL too, like the free one.

Is it possible? I’ve sent email twice to the WordPress Extend contact, but they didn’t reply yet, maybe they’re too busy uploading new themes ??