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dtrace on Linuxdtrace on LinuxPosted Sep 21, 2008 9:29 UTC (Sun) by paulj (subscriber, #341)In reply to: dtrace on Linux by zooko Parent article: KS2008: Tracing
The legal constraint on using dtrace or ZFS on Linux is exactly the same as the legal constraint on using a proprietary hardware driver on Linux. Uh, not really. DTrace is free software..
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dtrace on Linux Posted Sep 21, 2008 11:22 UTC (Sun) by Jonno (subscriber, #49613) [Link]
But it's not GPL compatible, so the *legal* constraints are the same.
Morally and technically it's another matter however, as the source *is*
dtrace on Linux Posted Sep 22, 2008 10:58 UTC (Mon) by paulj (subscriber, #341) [Link]
And yet Linux distros still manage to ship these proprietary, binary-only drivers, despite these terrible legal constraints.
With DTrace being free-software, there isn't even much of a moral hazard...
dtrace on Linux Posted Sep 22, 2008 13:57 UTC (Mon) by corbet (editor, #1) [Link] The number of Linux distributions shipping binary-only drivers has gotten quite small; there are good reasons for that.DTrace presents a different hazard; imagine a Sun-turns-SCO scenario, for example. The fact that Sun does not appear to be interested in taking that path now is irrelevant; neither was Caldera, once upon a time.
dtrace on Linux Posted Sep 22, 2008 14:54 UTC (Mon) by paulj (subscriber, #341) [Link]
There's no hazard from Sun, as the CDDL licensed DTrace bits can be combined just fine with GPL bits, as far as the former licence is concerned. The hazard is from a Linux kernel copyright holder turning SCO on Linux distributors, I thought we had established in an earlier discussion.
dtrace on Linux Posted Sep 22, 2008 15:42 UTC (Mon) by zooko (subscriber, #2589) [Link]
Wait, what happens if Sun decides to try to use all of its copyrights to sue Linux distributors or users or otherwise to do harm to Linux development? Haven't they already granted a permanent, irrevocable Free Software licence over the current versions of DTrace and ZFS, in the form of the CDDL?
I have a feeling that you already addressed this in your "What if Sun turns Evil?" article, but I don't recall any actual problems that could result from use of DTrace or ZFS source code.
dtrace on Linux Posted Sep 22, 2008 17:33 UTC (Mon) by njs (subscriber, #40338) [Link]
Well, there is Sun's ongoing refusal to answer questions like "Are you willing to grant a license to any ZFS patents you hold to other FOSS implementations?", which creates at least a cloud of uncertainty about what they might do if they became evil, or just decided that Linux was catching up with Solaris and threatening them.
Unless they have changed their mind and answered this at some point. I hope so -- haven't followed closely.
But paulj is right re: copyrights; Sun wrote the CDDL in such a way that combining CDDL and GPLv2 violates the GPL but not the CDDL. This has the same effect in practice as not granting permission, but it means that for copyright issues we don't need to worry about Sun-turns-SCO -- we need to worry about SCO-turns-SCO.
dtrace on Linux Posted Sep 21, 2008 12:43 UTC (Sun) by zooko (subscriber, #2589) [Link]
That's a really good point that DTrace is Free Software. I just now eventually came around to realizing the relevance of that in another post on this thread.
However, my point here was that resulting restrictions on use and redistribution are similar:
The copyright holder on DTrace has granted permission to use it in Linux systems, but the GPL which governs redistribution of Linux source code forbids redistributing derived works which include non-GPL'ed code such as DTrace.
This winds up imposing the same sort of restriction on users and distributors that a proprietary driver does: the copyright holder of the proprietary driver grants you the right to use it in your Linux kernel, but the Linux licence forbids you to redistribute it (assuming the current standard interpretation of GPL applied to this issue).
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