There have been debates about this before. Not too much agreement.
For what its worth, the AFS module and Caldera's netware file system
are distributed as kernel modules w/o source and not too many people
are up in arms. In fact I think Linus made some changes to the kernel
code to accomidate AFS.
Linus has made the statement that as long as you limit yourself to the
interfaces provided in kernel/ksyms.c, the module can be considered a
free-standing unit and not subject to the GPL --- just as a program
which is executed under the Linux kernel does not have to be subject to
the GPL.
At least in theory, the ksyms.c interface attempts to be much less fluid
that than rest of the kernel interfaces, so there is some prayer of a
chance that a module which is distributed versus one particular kernel
release will continue to work with future kernel releases.
It is certainly against the sprit of Linux to not have source to everything.
However, I think most linux developers, given the choice of having
an AFS module w/o source or not having an AFS module at all, would choose
to have the AFS module w/o source. I suspect that many people would
make the opposite choice, but I am only speaking about the attitudes
that I have observed on this mailing list.
That's certainly the choice I would make. RMS and others would make the
opposite choice, of course, but I believe it's this kind of flexibility
that will allow Linux to be much more useful than the HURD ever will
be. As much as I would prefer for AFS and the Netware client software
to be free, the sad fact of the matter is that it is extremely unlikely
this will be the case. In the meantime, I for one would prefer Linux to
have the functionality instead of remaining ideologically pure.
- Ted