I located MIT’s SITS timesharing system on PDP-10 backup tapes, and the author, Ron Lebel, kindly agreed to make it available to the public. It was created to replace the previous Logo-only timesharing system running on a PDP-11/45.
The main attraction of this system is indeed the Logo programming language. There are a few interesting options for turtle grapihcs: the old vector displays, the new raster displays, and Minsky’s 2500 computer. I added these features to SIMH so it’s now possible to run SITS.
More information can be found here: SITS - Computer History Wiki