Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
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you must not use any part of the materials used in or on the products for commercial purposes without obtaining a written license to do so from us . 

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. OPTIONS: ["Arbitration", "Choice of law", "Jurisdiction", "Limitation of liability", "Contract by using", "Unilateral termination", "Content removal", "Unilateral change", "None"].