Is His Communication Style Really a Negative?
As a person who has been accused of being unfriendly to others and who has actually been fired for such from a real, paying job, I'd encourage you to take a step back and consider that the very thing you see as problematic may in fact make him a huge asset to your team. Consider that the fact that he wants to offer feedback may be a sign that he's committed to a much higher level of quality than your other team members have previously encountered. The fact that he's willing to tell people where they could improve means that he can actually serve a valuable mentorship role if you can persuade the other artists to put on their grownup panties and take what he's so willing to offer.
In addition, it's quite possible that he offers frequent feedback because his greater experience has taught him where the pitfalls lie. Less experienced teammates might well discount or ignore his feedback because he may not be fully articulating the thought processes that have led him to point out things they think are trivial. Or possibly other team members don't yet have the experience to see why those things are not trivial. His experience may also be that trying to be diplomatic doesn't work, either because it doesn't yield the desired changes or because the communication he worked so hard to make "better" still offends people.
He's not Going to Change
In short, nothing you've said about his feedback style suggests that there is any meanness or anything self-serving about it. I would not expect that you'd get him to change his feedback style for a volunteer project. I consider it unlikely that he is not aware that other people consider his feedback style problematic, so if he is still doing it he is unwilling or unable to change. In my case, I finally came to the conclusion that if I held back on what I considered to be necessary feedback I was short-changing my employer, because all that experience and the willingness to share it is part of what I bring to the table.
On the flip side, this is a volunteer project and the other artists may well not be impressed with the opportunity to improve their skills by working with this talented person, particularly if they can't see his feedback as anything other than abuse. How willing are you to take the chance that they'll simply walk? How committed is he to the project? If they walked and you had to do it with just him, could you? If they walked, would he be likely to stay to the bitter end?
So Now What?
If you want to bring him on, I think you have one of two options.
I think the better one is to talk to the rest of the team and couch it as a fantastic opportunity to learn from his greater experience "yes, sometimes his enthusiasm gets the better of him and he says things in a way that I wouldn't have said it, but he's always going to be pushing us toward greater quality." If the team isn't fully behind that, don't include him unless you are willing to lose the other artists.
Tell him of your concerns and ask that all feedback he has about others on the team go through you. This makes the decision of what to share and how yours. If he is aware that others have a problem with his communication style, he might actually find this to be a bit or relief--he might be just as concerned as you are about his interactions with the other artists, but unable to stop himself from saying the things you fear he'll say.