Doesn't exist.
I don't know if this was ever common knowledge, but it's certainly not a new idea. Free software, per the Free Software Foundation, is only free if people are free to redistribute it commercially without having to pay the author. In a sense, every time you build a Drupal site for someone else for a fee, you are charging to distribute free software to them that was authored by other people while providing additional services to tailor it to their needs.