I just got an email from these people:
We’ve finished reading the abstract of your paper [title redacted of one of my papers already published in a highly prestigious journal] and will recommend it to our editors. If you are interested in our journals and want to publish it on our journals, please extend this paper and send it to us by our online submission system. All manuscripts submitted will be considered for publication.
My guess is that they are desperate for content, and are trying to have authors “extend” already-published papers and republish them. This seems like an incredibly bad idea, and likely to run afoul of copyright law.