[zanny]

You don't have to get consent from anyone without reusing, redistributing, or modifying their copyrighted materials.

A cleanroom reverse engineering is perfectly legal, without any "permission", in most countries.

[prewett]

Yes, but distributing the copyrighted art with your clean-room reverse-engineered engine is not legal. Hence, no art is available for this engine, and you have to procure your own copy of the art, presumably from the CD you purchased, in order to use the engine.