3. RESPONSIBILITY FOR EMPLOYEES AND SUBCONTRACTORS, INCLUDING AGENCY MEMBERS
If a User subcontracts with or employs third parties to perform Freelancer Services on behalf of the User for any Engagement, the User represents and warrants that it does so as a legally recognized entity or person and in compliance with all applicable laws and regulations. Further, at all times a User that agreed to perform services under a Services Contract remains responsible for the quality of the services and represents and warrants that User has entered into agreements with any such employees and subcontractors on confidentiality and intellectual property at least as strong as those in these Optional Service Terms.
it's a business to business agreement. a contractor is free to sub.
3. RESPONSIBILITY FOR EMPLOYEES AND SUBCONTRACTORS, INCLUDING AGENCY MEMBERS If a User subcontracts with or employs third parties to perform Freelancer Services on behalf of the User for any Engagement, the User represents and warrants that it does so as a legally recognized entity or person and in compliance with all applicable laws and regulations. Further, at all times a User that agreed to perform services under a Services Contract remains responsible for the quality of the services and represents and warrants that User has entered into agreements with any such employees and subcontractors on confidentiality and intellectual property at least as strong as those in these Optional Service Terms.
it's a business to business agreement. a contractor is free to sub.
https://www.upwork.com/legal#optional-service-contract-terms