This really sucks. But just because he has gotten a "license" from a musician friend does not mean that they can use/copy any sounds or melodies, and the company attacking him might have some kind of valid claim. Just a quick check of the first video I found from him had an intro which could be argued to be similar to George Harrison, Got My Mind Set On You for example.
https://www.youtube.com/watch?v=A2IVj4K2hLE https://www.youtube.com/watch?v=6ZwjdGSqO0k