Someone on an I visa can only work for the organization they were sponsored by. Your friend needs to consult an immigration attorney.
Attorney at law
Generally people on I visa have a US employer who files for them so they do not need a work permit
Alexus P. Sham email@example.com (917) 498-9009. The above information is only general in nature and does not constitute legal advice. It does not create an attorney-client relationship.
the status form associated with the visa is the permit.
NYC EXPERIENCED IMMIGRATION ATTORNEYS www.myattorneyusa.com; email: firstname.lastname@example.org; Phone: (866) 456-8654; Fax: 212-964-0440; Cell: 212-202-0325. The information contained in this answer is provided for informational purposes only, and should not be construed as legal advice on any subject matter.