You may have noticed that every time you upload a file to Moodle, you can say what the licence is. (See the screen-grab at https://docs.moodle.org/35/en/Upload_a_file_repository if you have never noticed this.)
There is a suggestion (MDL-64085) that we do the same for questions in the question bank. This would be a new field on the edit question form, and would default to 'All rights reserved', like for files. We would not do anything with this information. Just include it in any Moodle XML exports.
What do people think?