Specifically in Obj files, appgamekit (and only it) can accept 2 sets of UV in same vt line. 1st UV coords for texture 0; and second UV coords for texture 1 (lightmaps). 3D example "Metro theater" use this specific implementation of obj files for appgamekit. (I have a specific Obj export plugin for Ultimate Unwrap3D which supports it if the model/scene your convert has lightmaps .. thanks to the Unwrap3D author which has done it for me !).
But now i use my own B3D Loader which convert to OBJ for appgamekit with lightmaps support.