There are three lookup attributes obj_stakeholder1 to obj_stakeholder3. These don't take up a licence. The lookup used does require the user to be in PPM where they can be a 'view-only licence'. Otherwise, as David indicates a string text attribute could be used.
I personally like 'look-ups' as you may want to filter for all projects for Stakeholder A, for example, to provide them with the latest Status Report.