I've been reading through this thread for quite a while and I'd like to add a word.
Generally, the copyright law is a very complex field full of traps. In addition, once an international aspect is present, the number of possible consequences is virtually astronomical. Well, yes, a lot of work has been done to unify copyright rules globally, mostly as a result of the U.S. government effort. However, in the end it's national courts who have the last word in any particular case, and you can hardly predict which court would be the right one to hear and decide any possible future lawsuit. The legal practice in various countries still differs significantly. Nobody can tell with absolute accuracy...
I believe it's Paradox's best intention not to be too restrictive as long as modding remains basically a FUN, a kind of entertaining activity which we all love because it's so intelligent, so creative, and so inspiring. And I'm pretty sure that all modders maintain the same approach. That is not to say that any modder should resign on his right to be credited - for any good idea of any kind.
So I suggest that Paradox should consult their legal advisors and post a general statement that will protect
Paradox from possible attacks by
third parties. You must protect yourselves against accusations that you host a pirate hub. In very basic words, you should declare your preparedness to ban anybody or anything on the ground of copyright law violation and that you invite both forum members and third parties to inform you immediately if such a case occurs. (Most pirate sites start with similar statement...

)
That's the only thing that really matters. No kind of statement will ever protect you from any copyright lawsuit. You can only protect yourselves from accusation of supporting the intellectual piracy. And remain free of any commitment to protect your own copyright, as well as being cautious in exploiting any modders' ideas... because no matter what
YOU declare,
THEIR rights will remain the same.