You say it is an engine for making RPG's. A game engine can do anything, 3D first-person-shooter game up to just some fancy mediaplayer. All begins from abstract classes, and specializes to things like certain sound or graphics API. It can support many of them. At the present moment we don't know when or if we'll be adding SDL in the mix, even 2D can be done with OpenGL, using basic or GLSL rendering. Lastly all of the functionality should be crossplatform from the start, and possibly usable on mobile or android platforms. Unless engine was specifically written with all that in mind, it would be difficult to adapt.