So many thoughts, so little time today to type them.
But first, a disclaimer: this is not legal advice. I am not your lawyer. Do not rely on anything I say here.
Generally speaking, I don't see linking to copyrighted materials as a big legal risk. Courts have generally said that merely pointing out the location of pirated material isn't a copyright violation (though I haven't researched this point lately and could be wrong). And to the extent that it would be a risk, it could be mitigated relatively easily by adding a link somewhere on the forums telling aggreived copyright holders where to send their DMCA takedown requests (it's a little more complicated than that, but basically, if you go through a few hoops that lets copyright holders send takedown requests, you're pretty much immune to copyright claims based on what users post).
That's not to say that the admins can't or shouldn't say that links to pirated material aren't welcome for reasons other than potential liability.
I do think that "sharing copyrighted material" is a spectrum. All these are ways of pointing someone to a set of pirated rules:
- Uploading the PDF
- Posting a link directly to the PDF
- Saying that the rules can be found on <name of site here>
- Pointing out that <name of site here> has lots of copies of old games that one can download for free, should one be inclined
- Saying that one could probably find the rules with a quick Google search
- Observing generally that Google is a useful resource
The result in each case is basically the same—it's just a question of how much winking, nudging, and indirect reference is involved. That's not to say that people should be trying to find loopholes around Rule 4, of course. But I do think there's a fair question as to exactly what's forbidden in the spectrum listed above.
Also, I tend to be less in the "all copyright violations are bad!" camp than most, partly because copyright law is so complex and encompassing that many people violate copyright law without even knowing it. That includes the Unseen Servant forums. How many times have players or DMs on here found pictures on the internet then either copied those pictures here or embedded them in links? Unless those pictures were posted under the Creative Commons license or something like it, odds are very good that each of those infringes someone's copyright.
Another problem with copyright law is that the term of protection vastly outlives the usefulness or commercial availability of the material. If something is available on drivethrurpg, for example, then by all means, it should be purchased there, not downloaded from sketchypdfs.biz. But what if people want to play an abandoned game—one that was published by a now-defunct company and is not sold anymore? Is it morally wrong to grab a copy of that off the Internet, if someone with an old copy scanned it in? I don't think so, personally. Copyright law is meant to add to the body of creative work, not subtract. In this example, no one is left to complain about the copyright being violated. But I think the larger point stands even if the game technically belongs to a company that no longer sells it. If you can't buy it legitimately, I don't feel bad about getting a pirated copy. (See also: "abandonware" games.)
On whether "pay what you want" means "freely distributable": not necessarily, but it might. It's two different things that might happen at the same time. Pay-what-you-want means just that: I'll sell it to you for whatever you'll pay, even if that price is $0.00. But maybe I really want you to get it from me, not someone else. Maybe what's important to me is knowing how many people got a copy of my game. Or maybe I'm willing to sell it to you for free, if you tell me that's what you think it's worth, but I'm not so happy about someone putting it online where
anyone can download it for free without even having to take a moment to decide what they think it's worth. Just asking "what is this worth to you?" is psycologically powerful: the fact that anyone ever makes money from something that's "pay want you want" is proof of that. Redistributing "pay what you want" material can cut into profits and is a copyright violation—unless the author
also says, "and redistribute it however you like."
Then there are questions of whether you're allowed to change what you got, or build your own things based on it, or sell it (even if you got it for free). Like I said—copyright is complicated. It involves a whole bunch of different rights: not just copying, but distribution, performance, etc. A copyright owner can grant people permission to do one thing (e.g., make a copy) but not another (redistribute that copy).
Which brings me around to the Purple Worm thing. I think that's a clear violation of WOTC's copyright, despite their handwaving in the direction of the first-sale doctrine. But WOTC hasn't complained about it, and Purple Worm has at least made a claim that their use is permitted—specious though I may find it. So does posting a link to the Purple Worm 2e site violate Rule 4? Does mentioning that the site
exists violate Rule 4?