The code generator uses text templates as the foundation for the generated source code. The original templates for the Business Entity code generator can be found in the folder Consultingwerk\BusinessEntityDesigner\Generator\Templates.
If you want to customize the templates, e.g. use your own copyright header or a custom base class for the generated Business Entity or Data Access classes, you should create a copy of the whole template folder (all files) and make the modifications in your copy. Distribute this copy to your team mates (using your source code management utility).
The templates are identified by the file name (.template extension) only. In the Business Entity Designer options you just specify the folder that contains the template files.
The .readme files explain the tokens which are replaced in the templates based on your design.