Initially intended for use inside the Bell System, AT&T licensed Unix to outside parties in the late 1970s, leading to a variety of both academic and commercial Unix variants from vendors including University of California, Berkeley (BSD), Microsoft (Xenix), IBM (AIX), and Sun Microsystems (Solaris).

Does the license state that AT&T can reclaim copyright?

  • 2
    The agreements aren't, AFAIK, public except to the extent they've been introduced in court (that's generally true of private legal agreements in the US). So the place to start would probably be UNIX System Laboratories, Inc. v. Berkeley Software Design, Inc and possibly the SCO v. IBM mess.
    – derobert
    Commented Jan 18, 2019 at 18:06
  • @derobert Thanks for the link. But this sentence:Because this Berkeley Software Distribution (BSD) contained copyrighted AT&T Unix source code, it was only available to organizations with a source code license for Unix from AT&T. seems if Berkeley not remove all code from AT&T, Berkeley cannot distribute its Unix with BSD license.
    – roachsinai
    Commented Jan 18, 2019 at 18:26
  • Well, that's what was being litigated. They went to court and eventually came to an agreement (a settlement). That ends the dispute.
    – derobert
    Commented Jan 18, 2019 at 18:41
  • 1
    See McKusick’s retelling for all the history. Commented Jan 18, 2019 at 18:54

1 Answer 1



Part of the Settlement was "USL would not file further lawsuits against users and distributors", and you can not copyright something you can not litigate about.

113 of 76644 files in feeBSD grant use by the USL but are open licensed (BSD|Beerware|MIT|GPL|ISC|RSA).

git clone -q --depth 1 https://github.com/freebsd/freebsd.git
cd freebsd
grep -Ril "UNIX System Laboratories" | wc -l
grep -Ri "SPDX-License-Identifier:" . | grep -Pv "BSD-|Beerware|MIT|GPL|ISC|RSA|Binary"

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