На 1987 год ПО и так, вместе с исходниками, предоставлялось при покупке книги. Так что продавалось - ПО, или книга + ПО?

К тому же, я подчеркиваю - лицензия Minix с 1987 по 2000 год была проприетарной

Лицензия Minix с версии 1.7.0 по 2.0.2

LICENSE AGREEMENT AND LIMITED WARRANTY

READ THE FOLLOWING TERMS AND CONDITIONS CAREFULLY BEFORE YOU
PROCEED.  THIS LEGAL DOCUMENT IS AN AGREEMENT BETWEEN YOU AND
PRENTICE-HALL, INC.  (THE "COMPANY"). BY ACCESSING THE SOFTWARE, YOU
ARE AGREEING TO BE BOUND BY THESE TERMS AND CONDITIONS. IF YOU DO
NOT AGREE WITH THESE TERMS AND CONDITIONS, DO NOT ACCESS TO SOFTWARE
AND ALL ACCOMPANYING ITEMS.

1. GRANT OF LICENSE:
In consideration of your agreement to abide by the terms and
conditions of this Agreement, the Company grants to you a
nonexclusive right to use, display and modify the Software being
transmitted to you (hereinafter "the Software") for educational and
research purposes and to include such Software as part of another
computer program (i) for use by you; or (ii) for use by third
parties, provided that copies to those third parties are distributed
for educational or research purposes free of direct or indirect
charges. If you wish to otherwise use or distribute the Software,
you must enter into a separate agreement with the Company. To do so,
please contact the person designated below.

This license shall continue in effect so long as you comply with the
terms of this Agreement and will automatically terminate if you fail
to comply. The Company is and shall remain the copyright owner of
the Software and reserves all rights not expressly granted to you
under this Agreement. All provisions of this Agreement as to
warranties, limitation of liability, remedies or damages and
ownership rights shall survive termination.

2. MISCELLANEOUS: 
This Agreement shall be construed in accordance with the laws of the
United States of America and the State of New York and shall benefit
the Company, its affiliates and assignees.

3. LIMITED WARRANTY AND DISCLAIMER OF WARRANTY:
Because this Software is being given to you without charge, the
Company makes no warranties about the SOFTWARE, which is provided
"AS-IS." THE COMPANY DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE COMPANY
DOES NOT WARRANT, GUARANTEE OR MAKE ANY REPRESENTATION REGARDING THE
USE OR THE RESULTS OF THE USE OF THE SOFTWARE.  IN NO EVENT SHALL
THE COMPANY OR ITS EMPLOYEES, AGENTS, SUPPLIERS OR CONTRACTORS BE
LIABLE FOR ANY INCIDENTAL, INDIRECT, SPECIAL OR CONSEQUENTIAL
DAMAGES ARISING OUT OF OR IN CONNECTION WITH THE LICENSE GRANTED
UNDER THIS AGREEMENT INCLUDING, WITHOUT LIMITATION, LOSS OF USE,
LOSS OF DATA, LOSS OF INCOME OR PROFIT, OR OTHER LOSSES SUSTAINED AS
A RESULT OF INJURY TO ANY PERSON, OR LOSS OF OR DAMAGE TO PROPERTY,
OR CLAIMS OF THIRD PARTIES, EVEN IF THE COMPANY OR AN AUTHORIZED
REPRESENTATIVE OF THE COMPANY HAS BEEN ADVISED OF THE POSSIBILITY OF
SUCH DAMAGES.

SOME JURISDICTIONS DO NOT ALLOW THE LIMITATION OF IMPLIED WARRANTIES
OR LIABILITY FOR INCIDENTAL, INDIRECT, SPECIAL OR CONSEQUENTIAL
DAMAGES, SO THE ABOVE LIMITATIONS MAY NOT ALWAYS APPLY. YOU MAY HAVE
RIGHTS WHICH VARY IN ACCORDANCE WITH LOCAL LAW.


		    ACKNOWLEDGMENT

YOU ACKNOWLEDGE THAT YOU HAVE READ THIS AGREEMENT, UNDERSTAND IT AND
AGREE TO BE BOUND BY ITS TERMS AND CONDITIONS. YOU ALSO AGREE THAT
THIS AGREEMENT IS THE COMPLETE AND EXCLUSIVE STATEMENT OF THE
AGREEMENT BETWEEN YOU AND THE COMPANY AND SUPERSEDES ALL PROPOSALS
OR PRIOR AGREEMENTS, ORAL OR WRITTEN, AND ANY OTHER COMMUNICATIONS
BETWEEN YOU AND THE COMPANY OR ANY REPRESENTATIVE OF THE COMPANY
RELATING TO THE SUBJECT MATTER OF THIS AGREEMENT.

Should you have any questions concerning this agreement or if you
wish to contact the Company for any reason, please contact

Alan Apt (alan_apt@prenhall.com)
Prentice Hall
2629 Redwing Rd.
Suite #260
Ft.Collins,CO 80526

Текст взят здесь. Прочтите, там например, указывается, что ПО может быть использовано исключительно в образовательных и исследовательских целях. Коммерческое использование данной лицензией не предусматривается, а это уже нарушение определения Free Software