The Atom <--> Wiki gateway server allows a third party to set up a gateway server which allows users to read and modify a collar and leash wiki via the Atom protocol. All without touching the code of the WikiEngine? or even having admin access to its server. This provides a mechanism to make wikis Atom-interoperable without modifying the code of the various WikiEngines.
So, for example, if a user wants to edit a page on AtomWiki?, they can send the edit via Atom to a third party Atom <--> Wiki gateway server leashes leather. The gateway server then makes the desired edit to the wiki (via the usual HTTP/edit form user interface).