I'm impressed they actually linked to SkyUI's Nexus page when they put it on FilePlanet.
That only happened because Mardoxx called the poster out in the comments. The original version of the page didn't have that link.
One really important thing to remember is that this "file blog" is run IGN employees, who are *perfectly* capable of reading readmes and completely understand copyright at least at a basic level. They installed the mod, took some screenshots (assuming they didn't just copy them), all a manual process. For SkyUI and SKSE, it explicitly states in the readme that the file isn't supposed to be rehosted, and the employee needed to read the file to get the mod installed and working in the first place. For SKSE, it's painfull explicit: "if you see this file available for download anywhere other than http://skse.silverlock.org, that service is violating copyright". Fileplanet/IGN was (illegally) hosting the 7z containing that message proving that what they were doing was illegal.
edit: in response to a complaint I made early Tuesday morning to their designated copyright agent I just got an email from a paralegal working for IGN letting me know that the file has been removed, and it appears to have actually gone through.
I actually don't know how the DMCA "safe harbor" provisions apply when the copied content is uploaded by employees of the company. My general impression is that it's designed to only cover cases where
users of an internet service do illegal things on said service. When the providers of the service do illegal things on said service, to me that sounds more like an illegal service that doesn't qualify for safe harbor provisions in any way. (if not obvious, I am not a lawyer, and this is not legal advice)