The two now describe almost the same category of software, but they stand for views based on fundamentally different values. For the free software movement, free software is an ethical imperative, essential respect for the users' freedom. By contrast, the philosophy of open source considers issues in terms of how to make software “better”—in a practical sense only. It says that nonfree software is an inferior solution to the practical problem at hand.
We in the free software movement don't think of the open source camp as an enemy; the enemy is proprietary (nonfree) software. But we want people to know we stand for freedom, so we do not accept being mislabeled as open source supporters. What we advocate is not “open source,” and what we oppose is not “closed source”. To make this clear, we avoid using those terms.