Not sure I understand what you are asking- You do realize that anything posted on the internet is viewable to the world. If you click on the pics they will bring you back to the Quilt board- so PINterest is NOT claiming they made the quilts, NOT claiming it as their own work- they are just giving more exposure for quilts that have already been posted on the internet.
I personally don't use that site because when I went to sign up they wanted "permission" to access my address book and there was no way I was allowing that.