Today in an email message with the subject of [TUHS] Release of 8th, 9th and 10th Editions Unix, Warren Toomey announced that the Unix Heritage Society has now gained permission to make the source code of Research Unix's 8th, 9th, and 10th editions available for the usual non-commercial purposes. This apparently is the result of a significant lobbying campaign from a variety of Unix luminaries. The actual source trees can be found in TUHS' archive area for Research distributions.

Most people are familiar with Research Unix versions through V7 (the 7th Edition), which was the famous one that really got out into the outside world and started the Unix revolution. The 8th through 10th editions were what happened inside Bell Labs after this (with a trip through BSD for the port to Vaxen, among other things; see the history of Unix), and because Unix was starting to be commercialized around when they were being worked on by Bell Labs, they were never released in the way that the 7th Edition was. Despite that they were the foundation of some significant innovations, such as the original Streams and /proc, and for various reasons they acquired a somewhat legendary status as the last versions of the true original strain of Research Unix. Which you couldn't see or run, which just added to the allure.

You probably still can't actually run these editions, unless you want to engage in extensive hardware archaeology and system (re)construction. But at least the Unix community now has these pieces of history.