I'm fairly sure when you are buying physical copies of Linux distributions you are buying the service of compiling and copying it and providing physical media, the box, any manuals, etc. The source code at a minimum must be made freely available to others. That is, they aren't charging for the code delivered, but the delivery itself and the physical media.
You're permitted (under both the GPL and the DFSG) to restrict who you make the code available to, and to charge them for it. The only requirement is that the recipient have the right to further redistribute the sources, without being compelled to restrict who they distribute it to, or being compelled to charge for it.
That is, it is entirely legitimate and legal for me to make a Debian derivative where the only means of distribution is that I charge you $30/month for a CD of my distribution (including source to any patches I apply), and I don't distribute it otherwise. I just have to give you the right to rip the CD and put it online for free, if you so choose.
I'm not sure if this is meant to imply they don't have to offer the source in some form or just a clarification of my prior comment, but I think it's pretty clear from GPL 3.0 section 6[1] that it is required, and the most recompense you can get from this is "for a price no more than your reasonable cost of physically performing this conveying of source", as if it's network accessible it must be free. So, at least part of my prior comment was incorrect, you do not need to provide it free of charge, but the only charge you can require, and then only for providing it on a durable physical medium, is the reasonable cost of doing so.
Well, you can charge for the software as a whole, which I read your comment to claim you can't. I can absolutely say, hey, here's AwesomeDebianFork 1.0 with some custom patches on GPL code, you can get a CD set of binaries + source for $99. I don't have to resort to circumlocutions about service, and I don't have to make the source available to anyone else. (You are free to copy that source CD, though.)
The only thing I can't do is to say, the CD for AwesomeDebianFork 1.0 binaries is $9 and the CD for AwesomeDebianFork 1.0 sources is $90. (The GPL would reject this as not being "reasonable"; the DFSG would reject this outright for violating #2, "The program must include source code".)
> Well, you can charge for the software as a whole, which I read your comment to claim you can't.
Ah, yeah, that was an aspect of my original comment I wasn't thinking of, but was implying, and I had glossed over that in your reply. Thanks for correcting me and clarifying. :)
