In fact Linus has given blanket permission for anything which is linked
with the kernel dynamically (ie applications, libraries, kernel modules)
to not be under the GPL.
In the GNU/Linux system, applications and libraries are not linked
with the kernel--not statically, and not dynamically. They are linked
with GNU libc.
Non-free applications are permitted on GNU/Linux because the GNU
Project put GNU libc under the LGPL rather than the GPL.
A number of GPL-covered GNU programs are linked with some BSD files.
I used to think that the conflict was insignificant because our lawyer
told me that the BSD advertising clause was legally void under US law.
That meant it was a no-op, so it could not conflict with anything.
However, later I learned that in some countries the clause might be
enforcible, which means it is not a no-op, so it can conflict.
I hope this will get solved by Berkeley's changing its license.
