Whitelisting an IP or domain to bypass need for authorisation

at minimum, you must include an api key with all calls.
you can set up guest access (see: http://wiki.dreamfactory.com/DreamFactory/Tutorials/Setting_up_guest_access) which will allow access with api key only (no session information)
The api key can be included in the URL ( ?api_key=... ) so I believe this meets your requirements.