What an interesting topic!
I rarely buy patterns for quilts, because I never get around to making them!! One of the few I have bought & made was Pagodas by Debbie Bowles. After showing it at Guild, quite a few people requested a workshop in doing it, so I emailed Debbie & asked if that would be OK, and how much her patterns were. She was quite gracious, and not only gave me permission, but also gave us a special price on the patterns!
As has been said before, most designers are very good about that.
I also know, from one of our past Opportunity Quilts, that the magazines do state what the terms are for using their patterns. We did use one from an old copy of Quiltmaker magazine & again, we wrote for permission, telling them that we wanted to use it as a fund raiser. They seemed happy to give us permission.
When I was our newsletter editor, I was also a stickler for having permission to reprint items. I don't think I ever had anyone say no.