I have not found the answer to this question on the forum, so I decided to create this topic. Questions relate to licensing of downloadable models. I will give a probable example. For example the author publishes his model under Creative Commons Attribution (Author must be credited. Commercial use is allowed.) Its all ok, the model is 100% owned by the author and there are no problems with it. The developer likes this model and uses it in his commercial project, because the license allows such use of the model. At this stage, everything is fine, no one breaks anything. The author of the model learns that his model, which he published under a commercial license, is used by a certain developer in his commercial project and changes the license from commercial to non-commercial. Sketchfab makes this easy to do. After that, the author of the model sues the developer for copyright infringement. The developer is guilty, because he can not prove the opposite. Such a scheme can also be used for fraud and extortion.