Technically, DragonRaid is a discipleship program that is built similiar to a Role Playing Game. Game-wise, it is very simplistic. It is not open ended. It has very "on the rails", structured adventures because each adventure is attempting to teach the players. A lot of problems that people have with DragonRaid is based on their assumption that it is a game. It is a discipleship program that is structured like a game.
It is easy enough to take the world of DragonRaid and create your own, open ended adventures. It certainly has lots of open background for you to expand upon. When I was little, my father took the DragonRaid system and used it with several D&D adventures for me and my siblings to play through. It worked out pretty well.
If you've played lots of other RPGS, you'll find DragonRaid simple. It makes for a good "gateway game", teaching non gamers RPG concepts. I used it for years in my youth group as a small group activity. It was the BEST discipleship program I've ever had. The kids who participated in the DragonRaid program showed incredible growth. Hope that helps!