Copyright field in Project Properties should be specified for all uploaded scores.

I think most, if not all, scores uploaded to MuseScore.com should have a properly specified Copyright field. As appropriate the field might be "Copyright © [year] by [owner]", one of the Creative Commons designations, or simply "Public Domain".
If this information were included, then it would be clear what could or could not be done with a downloaded score for other than (always OK) private uses.
I would like to see thoughts about whether or not all uploaded files be required to have a "proper" Copyright field. Or, should a default be inserted into an empty field.
As i understand the current situation "Private Use Only" is the default meaning for a blank Copyright field unless the score is flagged as "Public Domain". But this flag doesn't go with a download,