[Inkscape-docs] report of difficulty uploading to gallery

Hi Friends, Lazur mentioned to me that he's trying to upload a new filter set to the gallery. If I understand correctly, it won't upload, and the license area becomes red. I've guessed it's because he needs to use a certain license for a filter set, but I'm not sure specifically which one. (Also not sure if that's a correct guess.) He had tried to use Public Domain. (See the Chatbox on the index page of Inkscape Community, for details.)

Thanks, brynn