Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
```
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 . 

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