> "The key differentiator between open source and free software is ideological."

You said...

> "I very much disagree."

You then explain your position with a link that says...

> "The two terms describe almost the same category of software, but they stand for views based on fundamentally different values. Open source is a development methodology; free software is a social movement. 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. Most discussion of “open source” pays no attention to right and wrong, only to popularity and success; here's a typical example.

For the free software movement, however, nonfree software is a social problem, and the solution is to stop using it and move to free software."

In other words, you link to an article that spells out in plain English that the difference is ideological. The approach to software is almost the same, but the reasons behind it differ. That's an ideological difference.