They provide the license to everyone to spread the word that they have apartment for sale by default. It's more resonable to assume that than anything else.
Google also indexes this data. Craigslist obviously doesn't own this data as they have DMCA practices in place. They can't claim DMCA and also say that the data is their data.
That is a power that, in the past, Craigslist has used for good. In this case, it's a power being used just for the benefit of Craigslist to protect its network effect incumbency, to the detriment of users.
Of course you're correct, but surely (under the active hypothetical of CL having a license to the users' data) it would fall to the users to sue PadMapper (which they almost surely won't, because they're happy having more interest in their rental).