Question

Do emulators/code for the traditional UNIXes like those AT&T ones exist?

Answer 1

emulators pretend to be hardware, while UNIX(es) is/are Operating System(s). So scratch that from the question (unless you want to ask whether there are e.g. emulators for PDP-11s, in which case the answer would be yes. Ask for specific machines, perhaps first on Google, and you can find for which other machines there are emus)

As to "code", please be more specific; what exactly do you want to do? Do you want to run a proprietary UNIX (which presumably will not be available for free online) on an emulator?

Looking at the history of the BSD family of kernels may be your best bet to get started, up to some point back to where source code is no longer available.

Answer 2

AFAIK, except for BSD and OSX, I believe that most everything else is AT&T derived. Solaris is/was available. You can pick up an Irix box REAL cheap. I don't know SCO well enough which branch it's from. I forgot which AIX is, but I suspect it's AT&T.

Answer 3

System V Unix code is around and it's great even after all these years. Older versions of Unix source code are also avaiable, I think. Posterior UNIX-based OS are generally proprietary, if my memory does not fail me.
On a completely unrelated side note, I was so happy that Doom3 source is around :-).

Answer 4

System III source code:
ftp://pdp11.org.ru/pub/unix-archive/PDP-11/Distributions/usdl/SysIII/

Answer 5

http://en.wikipedia.org/wiki/Lions%27_Commentary_on_UNIX_6th_Edition,_with_Source_Code

the WP page includes a link to the source code.