The fractions I've found of the 2.5 is on the CSRG #4 cd
https://vpsland.superglobalmegacorp.com/install/Mach/MACH_CSRG_CD.7z
You have to read the 404 to get the password. It changes frequently. 
I've been slowly trying to get 2.5 to build under Mt Xinu BSD/Mach. 
I've managed only the tools and bootloader so far.  I've just been busy moving offices the last week. 
Anyway in that directory is a bunch of other Mach stuff I've found. 
I also started trying to map the Mach 3.0 stuff 
https://unix.superglobalmegacorp.com/cgi-bin/cvsweb.cgi/?sortby=file&only_with_tag=MAIN&hideattic=1&hidenonreadable=1&f=u&logsort=date&cvsroot=Mach3&path=
Including BSDSS a unknown to me port of BSD to Mach 3.
It seems plenty of the Mach 1/2 stuff is hidden on CMU's servers in wait of the ATT v CSRG lawsuit.  And that everyone who worked on it left so it's locked away hidden. 
There is a vmdk of the mt Xinu installed that will run on qemu and most likely others as well.  So you can take it out for a test drive 


From: Chris Hanson
Sent: Sunday, June 23, 2019 12:46 PM
To: tuhs@minnie.tuhs.org
Subject: [TUHS] CMU Mach sources?

Does anyone know whether CMU’s local Mach sources have been preserved?

I’m not just talking about MK84.default.tar.Z  and so on, I’m talking about all the bits of Mach that were used on cluster systems on campus, prior to the switch to vendor UNIX.

I know at least one person who had complete MacMach sources for the last version, but threw out the backup discs with the sources in the process of moving. So I know they exist.

If nothing else, CMU did provide other sites their UX source package (eg UX42), which was the BSD single server environment. So I know that has to be out there, somewhere.

  — Chris

Sent from my iPhone