This is why if someone were the (usually) imaginary "Free Software zealot" that would like to prevent a private business from profiting off public work, it would be necessary for software not only to be under a Free license, but for the copyright assignment to be held by someone that agrees with said Free Software "zealot".
Or to put it another way: if you are contributing to a Free Software project and the copyright is held by some other entity to who you have duly assigned rights, then you may find that they decided to sell the right to use some of your contributions. So, be careful who you turn your copyright assignment over to.
