My company used to use a library which had an enforced license. It was a major headache -- and it was the simplest possible kind of license, where they sent us

My company used to use a library which had an enforced license. It was a major headache -- and it was the simplest possible kind of license, where they sent us an encrypted key file and we placed it on each server. As soon as we could, we negotiated an end to that. Instead, they ask us each year how many licenses we need and send us a bill. They have an audit right, but they've never used it. It won't be a problem if they do, because we are fully compliant.