May just be misunderstand here. For remote HTTP services, DreamFactory supports any authentication mechanisms that can be passed through curl options, headers, or parameters.
Many simple APIs support simple API key auth, or authenticating per call. If your remote API uses reusable sessions, you wouldn't necessarily have to reauthenticate on each call, but you would need to build some logic in either a script of your client application to get a session and store that information in a place where it can be reused. One possibility would be to put it in a user lookup in DF. Then in the service configuration, you could put the user lookup key in the header or parameter that sends the session information.