Wow, my surprise grows... I shall no longer add to this thread... Bye now.
http://www.kernel.org/signature.html

http://www.freebsd.org/doc/pgpkeyring.txt
* One example of a signed Linux Kernel path... there are many others:

ftp://ftp.kernel.org/pub/linux/kernel/v2.6/patch-2.6.9.sign
* One example of signed FreeBSD code... there are others:

http://taosecurity.blogspot.com/2007/11/updating-freebsd-70-beta2-to-70-...
Some examples of signed communications from FreeBSD & NetBSD:

http://www.freebsd.org/internal/ssh-keys.asc

http://mail-index.netbsd.org/netbsd-announce/2004/02/20/0000.html
On Dec 5, 2007 12:59 PM, Kevin Stam  wrote:
> For one thing, I think you're quite confused. Unless I'm missing

quoted text
> something, I'm not noticing the FreeBSD, NetBSD, Linux kernel developers

> "signing" their code, or doing anything particularly differently from the

> OpenBSD developers. Please explain.

>

> You've also conveniently ignored bofh's question. Why do you see this as

> being an issue? What risks does PKI mitigate? Did you just vaguely read

> somewhere in an advertisement about the supposed security benefits?