I've downloaded new 4.3.1 version and wanted to find which files were changed. Using VSS directory differences, I found that ALL files have been changed. Looking for details, I understood, that in most files only Copyright year was changed from 2005 to 2006. I think that it was a bad idea, because it make harder for users of DNN core source code to identify the changes.

In the environment with strict development procedures all source code changes should be done related to some change request(aka gemeni issue). Does a special issue to change increment copyright year exist and was approved?
I strongly beleive that there are more important open issues in DNN support, that are not implemented, because there is no available resources. 

I think, that from a legal point of view, changing the year in the file, where nothing else has been changed, also not correct. Keeping copyright notice in each separate file means, that each file considered as a separate item from the copyright point of view. So if a particular file wasn't change, there is no point to change the year when the file was modified.