Here's a strong counter argument to themes and plugins being forced to inherit GPL: https://enriquesthoughts.wordpress.com/2014/01/05/wordpress-is-gpl-must-your-plugin-be-as-well/

It's really ridiculous to enforce GPL inheritance on (all) themes and plugins. Just because a piece of software communicates with wordpress doesn't make it derivative of wordpress. Sure if you're modifying the 2015 theme than your product should inherit GPL, but if you create a new theme from scratch it quite clearly isn't.

Mullenweg and the Tavern being so dogmatic about this issue, to the point of blacklisting devs from speaking or getting press coverage just because they want to protect their work, will really end up hurting the ecosystem.

If you think premium plugins and themes are good for wordpress then you should allow those who create them the *freedom* to protect their work. If you really believe in the GPL then paid themes and plugins shouldn't even be allowed. It should all be distributed freely, just like wordpress itself. You can't have it both ways.

Maybe I'll create a nice reputable website that distributes all the premium GPL wordpress software out there for free. I can't be sued, any DMCA takedown requests are invalid, and everyones happy.....right?