I suggest you make a rule that says that tutorials submitted become the nonexclusive property of the site (copyright owned by author but nonretractable rights of publication given to the site).
I work with a lot of journals and documents putting them into e-publications, and it would be inconceivable for an author down the road to insist that his article is removed from a publication. Once it's published in a journal, the journal has it's own publication and republication rights.
That shouldn't take away the authors rights to republish or rewrite as well, but they should not be able to "pull" their publications on a technical grievance. |