On May 1, 2020, at 11:57 PM, Clem Cole <clemc@ccc.com> wrote:

[Note to Warren, we should put 4.1 in the browsing tree. The kernel is different enough from 4.0 and does have new utilities, although it was not nearly as different as 4.1c. The reality is until 4.2BSD came out with the networking support, most Vaxen running BSD were 4.1 not 4.0 based.

It is already there! The entry named "BBN's TCP/IP Code for the VAX” is 4.1BSD with the BBN TCP stack added. The changes to the kernel are just one or two dozen lines (all in sys2.c and main.c) bracketed in #ifdef BBNNET blocks. The actual network stack is in a separate build directory.