I'd say that if your project could be easily used for other games, then it's an engine - an example might be a game that has a level editor, scripting, and the additional aspects should be taken care of - like collision detection, media handling etc etc.
DBPro is not specifically a game engine, because you still have a lot of work to do, fast tracking is only really possible with simple projects or by using other peoples systems, plugins etc. It's really more like having the graphics and sound engine ready to go, that doesn't quite add up to a game engine - I mean nobody would call OpenGL and OpenAL together a game engine, those like DX, are libraries.

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