Like PG said, the only way you'd be able to do that is to create a heightfield in Terragen 0.9 and have your program able to interpret heightfield data. All Terragen does is render a picture, it does not create world data (such as a way to use the settings in TG2 to walk around in a 3D world - that would require a whole new engine to extract data and use it to create a world).
You can, however, generate a skybox from Terragen and use that as backgrounds if your program allows it.
