Embedded Linux Overview: Free Beer, Free Speech

An anonymous reader writes "Never one to have his thirst for 'free beer' quenched, LinuxDevices.com contributing editor Kevin Dankwardt sets off on a quest to determine just how much freely downloadable embedded Linux software flows from the taps of commercial embedded Linux vendors' websites -- and discovers that there's a lot more available than you might realize. Read Dankwardt's guide to 'free beer' (well, uhm, free embedded Linux, that is)."

Comments

Re:This is worth noting re. GPL

[renehollan]

Hmm... interesting. Is this type of behavior allowable under the GPL?

In a word, NO!

...and I'm sorry if I gave that impression. What you miss (and I failed to make clear) is the the Linux kernel is not licensed under the GPL. It is licensed under the GPL with a specific exception for kernel modules.

Now, there is nothing wrong with this, as Linus Torvalds can license his code any way he likes, and contributors have to accept that license for their contributions to be redistributed. Since some contributers prefer a pure GPL position, for political reasons, the means are there for their modules to check, at run-time, if any other non-GPL code has been dynamically linked in, at least that is my understanding. I don't know if this technique can apply to any contributed kernel code, but I see no reason why it couldn't in practice.

It is my understanding that RMS is very upset about this particular exception, but that should come as no surprise. It has led to production of non-free drivers within kernel modules with minimal "free" applications under the misleading notion that the code (all of it) is free. I'm told that NVidia does this with some of their video drivers, and RMS considers that very unfriendly, to the point of NVidia being hostile to the free software community (Disclaimer: I work for ATI, a competitor of NVidia, but these comments are entirely mine and not representative of any position ATI might take).

But, the fact remains, proprietary kernel modules or not, if you distribute binaries of the Linux kernel, even if unmodified (your mods being entirely in kernel modules), the GPL obliges you to either (a) distribute the source, (b) offer the source to anyone who asks (not just the recipient of your binaries) and has received the binaries, or (c) point them to a well-known location where they can be found. Option (c) is only available for non-commercial redistributors.

Contrary to popular belief, this does mean that a pointer to an FTP site you maintain is not sufficient complience unless that's where the binaries came from -- that is you can't ship CDs of binaries with a pointer to an FTP site as the only means of obtaining source, though it is perfectly acceptable to do this as an alternate means.

Now, the GPL strikes me as a little vague when it comes to inter-process communication between cooperating processes as part of a whole. Tom Christiansen's "GPL-freeing" socket wrapper around readline() is an example of it. While it may be legally complient with the GPL (though I am not a lawyer and you should seek specific advice from your legal council), it is generally viewed as deceitful and unfriendly by many.