I'm just saying, if the guys subsequently decided they wanted to do more in the future - there's nothing wrong in that.
Unfortunately the apparent existence of promotional material touting their services around France suggests that that decision has already been made.
Like I said, nobody has a problem with them making music. The problem is the way it has been handled by whoever does their publicity, as the current evidence suggests that they have arranged this supposdedly "one off" event for charity as a means of gaining publicity for what is in fact an entirely commercial enterprise.
Just my opinion, but my opinion is that it stinks.
And again, for the avoidance of doubt, this is not directed at the musicians.