I'm going to respond from a human point of view and not a technical point of view.
I've been searching for houses recently on Craigslist. There are a couple of real estate agents who post ads on CL with a link to their site. When you click the link, you get a lightbox requiring that you fill out the lead form to be able to see the details of the house. I do one of two things:
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I open up IE in private browsing mode and paste in the URL. The private browsing mode has something that prevents this script from running and I can see the house details just fine.
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If the house address is not provided in the CL ad, I'll copy the image URL of one of the CL photos and put that into a Google reverse image search. I'll find a different website that has posted the same house and use their site that doesn't require me to register. (I realize this may not happen in your scenario above).
I agree what the other people say about not wanting provide one thing to Google and another to users, and wanted to add that people will try to find ways around the registration. I don't have a solution for you, sadly.