Re: "Freedom in this case means that you can modify the software"
No, it is you who doesn't get it - even when it's been explained several times to you.
If free and open software didn't exist, then MS would probably still "own" the desktop - and Internet Exploder would probably still be "the one and only web browser", yada, yada, yada. Yes, I know things have changed, but lets stay in the context for a moment.
We've seen exactly how things work when one player has too much control of a market - and if the players have similar interests, it can work when there are 2 or more dominant players as well. Microsoft of the 80s and 90s was dead against standards - because standards allow the user choice, and user choice means you don't own them (hence why MS put so much effort into knobblinng Open Document Standards). We saw exactly what that meant when MS was at it's peak - blatant abuse of it's position so that users did not have choice. So you say that users have freedoms - they choose to use Windows because it works for them. Well that's a false argument - in a truly free environment that would be a valid argument, but it still isn't because MS still has significant market dominance on the desktop. In the corporate world, people use Windows because MS has engineered it so that it's "difficult" not to. In a free world, many of those businesses would still use Windows, but at the moment many use it simply because it's "too hard" not to - because MS's dominance from the 80s and 90s has still not been adequately reigned in.
Let me give you a specific case ... How many alternatives are there to running a Windows server to run your network of Windows desktops ? Can't think of many ? Perhaps you can't think of any ? That's because when there were alternatives, MS used dirty tricks to kill off any competition. Once they had near 100% control of the Windows server market, they were then able to leverage that to make it really hard to use non-Windows desktops - or at the very least, distort the market in their favour. This isn't conjecture, they were found guilty of it and that's why they were eventually forced to document their network protocols and make that documentation available on a fair basic to anyone. But because their position was so entrenched, they still have that dominant position today.
So one of the freedoms people talk about is that they can choose to run (say) a Windows server, or they can choose to run a different server and still have the network work. That way, MS have to compete and provide something that people think it's worth paying for, rather than provide the most rubbish crap they think they can get away with given that many people don't really have any choice.
And that sort of freedom only happens if there's a working marketplace with multiple viable offerings. And that's why the likes of MS, and now Google, and Amazon, all put so much effort into blocking that free market as much as they can get away with - and they have got away with a lot of illegal activities because authorities around the world have been far too slow to take action. Unfortunately, by the time action is taken, and in particular any corrective measures imposed, the damage is already done - typically the competition has long since gone out of business.