If the author has ethical concerns with companies using their work there's a simple way to make that explicit and unambigious – the license. No one can read their mind otherwise.
If you consult with someone over their project, then proceed to fork it behind their back, that's just being a dick, even if it was perfectly legal. We should not accept that kind of behavior. And that's even ignoring that the consultation was unpaid and the project was actually even stolen.
