I've found a couple my fics there. Linkage:
Here's a post with info
Here's a discussion on FFA
And the tumblr tag might be useful for finding further infos
EDIT: So while the PDF downloads are not free and ask you to log in, the mobi downloads work without login. (And look suspiciously like AO3's mobis.)
EDIT2: It starts to look more and more like a scam page going for credit card numbers and emails/passwords than a pirate site. Maybe fanfic is just collateral damage, since they've got loads of popular published works on there as well, which seems better-suited for the scamming thing. Whatever you do, don't use real email addresses with them, and only the pen name they already know, not your real name.
Another discussion here
And more about the scam behind the page
And another writeup by an AO3 staff member
EDIT 3: Apparently they've taken everything they got from AO3 down. \o/
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