The resounding "No!" answer to Should I feel guilty for one off contributions? raises the question, for me, of how easily a user could become a contributor to a given project.
"Easily" is obviously very difficult to quantify here. The barriers to contribution for an advanced user of the project may be different to the barriers encountered by a technically advanced user who is less familiar with the project, for instance.
Are there any studies or proposed frameworks for measuring the ease of contribution or barriers to contribution of FLOSS projects?