This page lists articles which use the legacy-style XML listings rather than the appropriate template version - see Wikivoyage:Listings. Since these have all been eliminated once, any new XML listings are almost certainly copyvios from another site and should generally be reverted.
This category is automatically added to any XML listing via the Template:Listing-legacy template.
This website uses the Wikivoyage API to get and display all the information you see. This is the MediaWiki API, which is a general API for accessing data from Wikimedia projects. You can find information about it here: MediaWiki API.