I didn't log in. For almost all of these they detect that I'm connecting from my campus IP block and unlock everything.

I accessed over a vpn link into campus, signed-in by my user ID. The md5sum of the link provided above (and the others in the thread) are identical to the copy I downloaded from my campus IP block. Unless you're also on the campus of Iowa State, I don't think they're watermarking this paper.

Distinguished editors strap Finster into vacuum target chamber...

"Come now, editorial board of Nature. Do you expect me to pay for a subscription?"

"No, Mr. Finster -- we expect you to fuse!"