If you intend to set up in the business of publishing and selling resources you ought to familiarise yourself with the laws related to doing so. It amazes me that anyone with at least a first degree can apparently be oblivious to issues of plagiarism and copyright. I understand there may be confusion due to the many resources on TES in breach of copyright and it could be argued that TES has a duty to support teachers by bringing to their attention that ALL parts of their work should be either of their own creation or licenced for their commercial use. It would appear that TES do not do this because they profit from any sales and perhaps believe that any legal dispute will be palmed off to the author rather than them. This isn't likely to change until such time that a large publisher deems it worth their while to take action. If and when that happens it will be interesting to see whether the action is taken against an individual author or TES and what the knock on implications of that will be. In the meantime you can choose whether to do things legitimately or join in with what is effectively the piratebay of teaching resources. Good luck.