From what I've read about Magma, Vander says he pretty much "channelled" those Kobaian lyrics, which to me implies they aren't a literal language, but more like some sort of dream-speak or glossolalia. Or maybe you can think of it as composed music for the human voice (bit like Stockhausen's choral works really.)
Though a lot of it sounds like German to me (Christian Vander is German, isn't he?)