Dirk BWhen it comes to WordPress Plugins and Themes, they have to be released under the WordPress GPL license. See https://wordpress.org/about/license/.
Envato’s license only covers items where copyright can be claimed eg. images or non WordPress scripts etc. See Envato knowledgebase https://help.market.envato.com/hc/en-us/articles/202501064?_ga=2.266354634.577689901.1513537155-1604268018.1513076182 and I quote “Authors of items made for GPL-based platforms can also choose to offer some individual items as 100% GPL. This applies only to WordPress themes and plugins currently. “. There is an argument that the CSS and JS files included in plugins and themes are not covered by GPL, however that argument does not hold as you cannot seperate the CSS and JS from the PHP part of the plugin. All three elements has to be provided in order for the plugin or theme to operate.
The plugin or theme also cannot be used on its own, it has to be installed on the WordPress platform and by extention utilises the same GPL license as WordPress itself.