Crazy, isn't it, when you think what Wikileaks get away with!
Out of interest, some forums avoid the fair use issue by changing the thread creation screen. Have you considered doing that?
A maximum limit on the Title of thread (ideally NOT HTML enabled), and body of thread (again ideally NOT HTML enabled), with the Source and Source URL fields left as the are, is more than sufficient for anyone to open a discussion topic, provide a link to the source article, offer an opening question or viewpoint and so on.
I don't know if this is possible in your configuration but one of my customers had a forum where new threads could have full HTML in the opening posts - and a spammer created an iframe and hosted some really pornographic content in it so visitors to the site opened an innocent conversation only to see at the top of the page, a pretty offensive pornographic video. What's worse, the video was actually uploaded to his site so his bandwidth usage went through the roof.
I'm only thinking, there's no real need for people to quote verbatim from news sites, or reproduce the HTML, or even excerpt, from a copyrighted source so if you wanted to stamp that out you could possibly just turn the HTML and excerpt options off, on new threads.
Actually, I like our system pretty much just the way it is. We may have some upgrades in mind, but I’m not thinking of making any major changes in the way we operate. It works. In fact it works very well. And I’m not worried in the least about our funding. I’m not in it to get rich and our users are providing plenty of money to cover our needs.