FreeBSD licence and 'the advertisement clause'

[Theo Markettos]

I'm looking to incorporate some source from FreeBSD into a project of mine
under the GPL.  I see that Berkeley dropped their requirement on the
advertising clause which makes FreeBSD code compatible with the GPL.  The
main FreeBSD licence doesn't include the advertising clause.

However, much of FreeBSD's source still includes the advertising clause. 
For example src/sys/net/if.h and src/sys/net/radix.h in source checked out
of CVS a few days ago.  Most of these are for Berkeley, although there are a
few for other individuals.

What is the licensing position?  I see that:
ftp://ftp.cs.berkeley.edu/pub/4bsd/README.Impt.License.Change
suggests the advertising clause may simply be deleted - but it's been 4
years since this was issued and the code is still contradictory.

Thanks,
Theo

-- 
Theo Markettos                 theo at markettos.org.uk
Liphook, Hampshire, UK         theom at chiark.greenend.org.uk
                               http://www.markettos.org.uk/