When an end user is accessing the 3rd party application and is authorizing it later on, it's usually expected that the user is relying on a browser. However, supporting other types of end users is easy enough. Writing the client code that processes the redirection requests from the 3rd party application and AuthorizationRequestService is simple with JAX-RS and additionally CXF can be configured to do auto-redirects on the client side.
Also note that AuthorizationRequestService can return XML or JSON OAuthAuthorizationData representations. That makes it easy for a client code to get OAuthAuthorizationData and offer a pop-up window or get the input from the command-line. Authorizing the third-party application might even be automated in this case - which can lead to a complete 3-leg OAuth flow implemented without a human user being involved.