"Assume the following scenario : I download a template from the template catalogue and deploy this for a customer as is. I make some simple modifications to the menus and fill the template up with new content. In fact I did not made a template from scratch but used the existing template from the catalogue. Is this action subject to a commercial offering ?"
No, it is not subject to commercial offering. As a Developer, you are free to remove our logo and copyright from our templates for client websites, no problem. There should be instructions for you to remove the copyright removal in the Member Area. (Top Menu >> Dashboard >> Member Area).
I'll give an example of commercial offering:
You create a template site call "Zasada Template Club" and use our YJSG framework for your templates for everyone to download or purchase. In that case, you we ask you to retain visible "Powered by YJSG Framework logo".