MGR, sometimes said to be short for “ManaGeR”, sometimes short for “Munger”, is a simple network transparent window system. It was originally developed for the Sun 3 series of workstations by Stephen Uhler and colleagues beginning in 1984 while at Bellcore (later Telcordia, now part of Ericsson) and later enhanced by many others.
The window system ran on many different hardware platforms, at least these: Sun 3/xx workstations running SunOS, which was the the original development platform, Sun SPARCstations (SunOS and then ported by me to Solaris), Intel x86 based PCs (Coherent, Minix, FreeBSD or Linux), Atari ST (under MiNT), AT&T UnixPC (SysV) and the Macintosh.
I had never heard of MGR before, so this was a great read.
I have mentioned it here in the past in the comments here:
The source code is here I also have a forked copy some updates where made a few years ago when I talked to the guy who put it up on github, the mouse support probably still has some issues though:
MGR is similar to the window manager on the AT&T Unix PC and the Unix PC can run MGR with some modificaitons… note the above code did compile when I played around with it a few years ago.
It would be a pretty decent UI for retroBSD etc… anyway the above code runs in a window hosted on X11 so its quite easy to play with.