It's like the US constitution and the bill of rights. Everything in the bill of rights is technically redundant and covered by principles already expressed in general form in the main constitution.
And yet that isn't actually good enough. Those general principles, being general rather than specific, require the key word, interpretation, in each new specific context. And different people with different goals can and do always ALWAYS warp interpretation in infinite ways that are all perfectly reasonable sounding on their face, and yet someone else can always produce a totally different interpretation, which also holds together.
Can you give any examples of software projects or licenses in which there's room for genuine disagreement in interpretation of these rules? I'm having trouble imagining it.
Does a licence that says "you must distribute the source unmodified, but you're allowed to distribute patches with it and a build system that applies them" count as free?
The DFSG said yes.
Does a licence says "you may modify this and redistribute it as much as you like, but if you put it on a CD then everything else on there must also be free" count as free?
You would have to compare them at the time. Things have changed. At the time Ian felt it didn’t do enough. Revisions and decades later it’s basically parity.
I don't understand what the author means here. What is unclear about the four freedoms? To me, Debian's definition looks redundant.