Net/2 was supposed to be the `uncontaminated' source code written by CSRG at Berkeley and others. However, when BSDi released their open-source product BSD/386, USL sued them because it was based on Net/2 and USL believed that portions of Net/2 were contaminated.
When the case was settled out of court in 1994, Berkeley and BSDi agreed to stop distributing the following files from Net/2:
/sys/kern/init_main.cThis agreement has now been made public, see this article on Groklaw.
and the cpio source.
For more information about Net/2, see Twenty Years of Berkeley Unix by Kirk McKusick. You may also like to read Kirk's comparison of Net/2 and 32V, made at the time of the lawsuit.