It's more than freedom of the mind--it the freedom to use and modify tools to do as you see fit. Software isn't the only industry that necessarily harmed by "closed" tools--Ivan Illich started making this point in the 1970s. If workers completely lose control of their tools, they necessarily lose freedom.
I don't buy it. A designer with Photoshop is no more empowered then a designer with Photoshop and its source code. The only people source code matters to (and helps) is programmers, but then we start leaving the realm of the FSF and start entering the realm of open source, which is rooted in practicality.
