I'ld need to know your situation a little better.  What do
you mean by 'touches Plan 9 code' or 'touches GPL code'?

If you are writing code that just links against our code and are just
releasing the source (or unlinked object files), our license doesn't
apply to you at all, i.e., you can do whatever you want with the code.
If you release it under BSD and want it to be part of our Plan 9
distribution, I'll have to keep it apart (in its own directory) and
include the BSD license in that directory.  That's because, the
BSD requires the list of conditions and disclaimers to stay with
the source code.  That would be fine with us.  We release stuff
under GPL, LPL, and a few other licenses on our CD.  It just
has to be kept separate.

If you are the only author of the code, you can also release it under
as many licenses as you want.

If you desire it to be part of our distribution and not kept
separate (i.e. so that other Plan 9ers can mix it into their
LPL licensed code) you can release it under the BSD (and/or GPL) license
to everyone else and contribute it to Plan 9 under the Plan 9 license.

I understand the fear of the legal language in our license.  I
would have used BSD if my lawyers had allowed it.

The bad part about multiple licenses is figuring out what to do
with updates.  If communities using very different licenses
contribute code back to you under their own licenses, then you
start having to keep very distinct records of your own since they
may have mixed in GPL's or LPL'd or BSD'd code.