He doesn't. I don't believe he's ever really had issue with programmers selling their labor. What he's objecting to is the idea of proprietary software; that is, the idea of software that the end user cannot see the source code to, and cannot modify for their own purposes if needed.

"You're free to stop using Skype any time if you don't like the terms."

At one point in time, the terms to using Skype could be agreeable to me, and so I invest in using it, get my friends using it, and use it for my business. Then later, those terms change, and because I do not have any rights to the code or do not have any of it under my control, either I have to spend a lot of time, effort, and money to replace Skype with something else, or just suck up and take it.