I did just got my theme taken down from themeforest. The because an author from codecanyon claimed his plugin was included in the theme without an extended license.
However, I have purchased an extended license some time ago, so I sent the Envato staff my license purchase verification.
The staff still wont accept this, saying, she also want a written permission from the plugin author.
Does this mean everyone including a plugin, e.g. a slideshow, both needs to purchase an extended license, and then also have a written permission to use it in their theme?