As long as you call
glEnableClientState(GL_VERTEX_ARRAY);
glEnableClientState(GL_TEXTURE_COORD_ARRAY);
glEnableClientState(GL_COLOR_ARRAY);
glMatrixMode ( GL_PROJECTION );
glLoadIdentity ( );
glOrthof ( 0, GetVirtualWidth(), GetVirtualHeight(), 0, 1.0f, -1.0f );
glMatrixMode( GL_MODELVIEW );
when you are done you could probably get away with it. Make sure you draw things in the right order, since at the beginning of App::Loop() the back buffer is blank, Render() draws all the AppGameKit internals to the back buffer, and Swap() puts it on screen then clears the back buffer ready for the next run through. So you'll probably want to draw 3D before Render().