As it says in the Licence page, 2. Restriction on Use:
[quote:3vi5clnw]Licensee may not superficially modify the Licensed Content and sell it to others for consumption, reproduction or re-sale. For example, but without restriction, Licensee may not resell audio tracks as backgrounds, hold music, ringtones etc.
[quote:3vi5clnw]Licensee may not distribute Licensed Content in a manner meant to enable third parties to create derivative works incorporating Licensed Content.
So you CAN change assets but you CAN'T sell those assets back