According to Clause 2 the agreement states that you give them permission to sub-license your art. So yes they can sub-license your work.
For how long? Your work can be sub-licensed for as long as the agreement exists unless either you or the company terminates the agreement via a 30-day notice to the other party. If the agreement is terminated, then they cannot sub-license your work.
What should you do to avoid sub-licensing? You can ask the Company not to sub-license or you can require them to ask for consent from you before sub-licensing.
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