It's not branded as D&D, but yeah, it's a D&D variant. It's not a 5E variant (it predates 5E), more of a 3E/4E variant. But I'd say it's as much D&D as 5E is--after 4E, 5E took the left fork, and 13th Age took the right fork. Well, 1E did; I haven't seen 2E.