dalcarr

Not a lawyer, but studied IP law in paralegal courses: anything produced in the context of employment is considered the IP of the paying party, so the “voice” of the character, as an extension of the character, is probably owned by the studio

I’m not familiar with the stream, but there would be a number of exemptions/loopholes. He might have written/verbal permission to use it (it’s essentially free advertising for the game), it may be written into his contract that he can use it other places, or the company may not know/care (again,free advertising/not hurting them)