Just going from the specific to the general, and at the risk of derailing this thread completely, but it is important, do you think therefore that we live in a plutocracy, and that the principal means by which we are controlled by the wealthy is through fear of litigation?
As regards to writing game materials and, well, writing anything, fear of litigation aside, I do not want to plagiarize what someone else came up with or wrote because I respect that person's right to get credit and profit from that idea. And because if I come up with a cool bit of flavor I write about, I know I would feel upset if someone took that from me. For me, the main reason I do my best to respect copyright laws is not because of fear of getting sued (although of course I don't want to be), but because even if copyright laws are are flawed (and I do believe they are), the intent of those laws is to protect artists and writers and their creations, and I respect and agree with that intent and thus agree to abide by those laws.
Writing, say, an OGL game, yes, you are using mechanics and such somebody else made, but hopefully putting your own spin on things (and of course using the OGL, which requires giving the credit and legally forgoes the profit (save indirectly)).
Yes, because, as they say, "there is nothing new under the sun," you might accidentally repeat something very similar to what's been done. You can't necessarily avoid that, but if your intent is not to steal, then hopefully you can prove that in the unlikely circumstance that you are "caught."
On another note, following along with what Dale said, the intent of OSR isn't "rules can't be copyrighted," it's "mechanics can't be copyrighted." There's a difference.