I usually use the term "REST" instead of RESTful - I know and understand the benefits of pure REST but I choose JSON over XML every time I can. Not to mention suboptimal support for PUT / DELETE / ... methods in Apache.
[1] https://www.ics.uci.edu/~fielding/pubs/dissertation/rest_arc...
That said, JSON is just an encoding format. The actual response format is not "JSON", but the specific structure that your clients are expecting to receive (even if it is encoded in JSON), and that can certainly have links.