You mean because the CDDL files would have to be licensed under GPL, and that's not compatible with the CDDL? I assume MIT-licensed files can be relicenssd as GPL, that's why that mix is fine?
You mean because the CDDL files would have to be licensed under GPL, and that's not compatible with the CDDL? I assume MIT-licensed files can be relicenssd as GPL, that's why that mix is fine?
Yes, if ZFS (CDDL) was integrated into Linux (GPL) then the GPL would need to apply to the CDDL files, which causes a conflict because the CDDL is not compatible with the GPL.
This isn't a problem integrating MIT code into a GPL project, because MIT's requirements are a subset of the GPL's requirements so the combined project being under the GPL is no problem. (Going the other way by integrating GPL code into an MIT project is technically also possible, but it would covert that project to a GPL project so most MIT projects would be resistant to this.)
This isn't a problem combining MIT and CDDL because both lack the GPL's virality. They can happily coexist in the same project, leaving each other alone.
(obligatory: I am not a lawyer)
And that's why zfs inches along with a fraction of the progress it could have had for decades.
This lack of required reciprocity and virtuous sounding "leave each other alone" is no virtue at all. It doesn't harm anyone else at least, which is great, but it's also shooting itself in the foot and a waste.
It's not an issue of GPL virality because the CDDL-ed code is not derivative of GPLed code and thus out of scope for GPL.
The problem is, IIRC, that GPLv2 does not allow creating a combined work where part of it is covered by license that has stricter requirements than GPL.
This is the same reason why you can't submit GPLv3 code to Linux kernel, because GPLv3 falls under the same issue, and IIRC even on the same kind of clause (mandatory patent licensing)
> The problem is, IIRC, that GPLv2 does not allow creating a combined work where part of it is covered by license that has stricter requirements than GPL
That is part of the virality: the combined work is under the terms of the GPL and therefore cannot have additional restrictions placed on it. If the GPL wasn't viral then the GPL code and CDDL code would both be under their respective licenses and leave each other alone. The GPL decided to apply itself to the combined work which causes the problems.