@LANthus Has he contacted those who are publishing his work without attribution to no avail? If so, send them a "Either pull these down, or pay my licensing fee" mail and attach an invoice for their usage with a pay by of 14 days. And before that, grab copies of the site through archive.org for potential evidence. See if the site owner is listed on a who is, so you can send an actual physical invoice.
@LANthus 👍
@PaulFerence thank you, this was pretty much the course of action I was going to sugest he take, but I really wanted some extra input