OK, the official answer is, just like with any other product, it is the responsibility of the individual to have secured the rights to use whatever he/she is using. There will be no question made by either Renderosity/Edgenet, E-on Software, or those personally in charge of the Vue contest as to whether someone has obtained the right to use any model in his/her contest entry. As with all art projects of this nature, by submitting something you have either implied or stated that you have the rights to use such a thing, for such a reason. And that's as "official-sounding", as I care to get....