Given that we are shown that Duke is older than Dick and discussed his time in the service, then that Jason was the first Robin and is older than Dick and Barbara, I would say it's canon. However, you don't have to take my word on it, the first series was well drawn and written, completely worth reading.
It is strongly tied to Batman: TAS, but also shows a good grasp of 80s comics and a certain amount of 90s comics.