On Sun, 25 Apr 2021, Vagrant Cascadian wrote:

> On 2021-04-25, Jack Hill wrote:
>> I'm working on packaging the Argyll Color Management System for Guix. To
>> build, it uses the Jam tool, which has the following license:
>>
>> ```
>> This is Release 2.5 of Jam, a make-like program.
>>
>> License is hereby granted to use this software and distribute it
>> freely, as long as this copyright notice is retained and modifications
>> are clearly marked.
>>
>> ALL WARRANTIES ARE HEREBY DISCLAIMED.
>> ```
>
> Permission to use, check.
> Permission to study, probably(?)
> Permission to share, check.
> Permission to modify, .... ?
>
> Is it even free software? There is no mention of modification which
> doesn't appear to be free by my layman's reading...

I do see a mention of modification "…modifications are clearly marked." 
Compare with the gnuplot license, for which modifications can only be 
distributed as separate patch files

/*[
  * Copyright 1986 - 1993, 1998, 2004   Thomas Williams, Colin Kelley
  *
  * Permission to use, copy, and distribute this software and its
  * documentation for any purpose with or without fee is hereby granted,
  * provided that the above copyright notice appear in all copies and
  * that both that copyright notice and this permission notice appear
  * in supporting documentation.
  *
  * Permission to modify the software is granted, but not the right to
  * distribute the complete modified source code.  Modifications are to
  * be distributed as patches to the released version.  Permission to
  * distribute binaries produced by compiling modified sources is granted,
  * provided you
  *   1. distribute the corresponding source modifications from the
  *    released version in the form of a patch file along with the binaries,
  *   2. add special version identification to distinguish your version
  *    in addition to the base release version number,
  *   3. provide your name and address as the primary contact for the
  *    support of your modified version, and
  *   4. retain our contact information in regard to use of the base
  *    software.
  * Permission to distribute the released version of the source code along
  * with corresponding source modifications in the form of a patch file is
  * granted with same provisions 2 through 4 for binary distributions.
  *
  * This software is provided "as is" without express or implied warranty
  * to the extent permitted by applicable law.
]*/

ajam clearly marks its modifications by including this in its readme:

"""
This if "Argyll-Jam", a simple derivative of the "FT-Jam" build tool, based and
100% compatible with Jam 2.5. See http://www.freetype.org/jam/ for more
details about FT-Jam.

This is the "FT-Jam" 2.5.2 release, with minor ArgyllCMS tweaks,
and the ArgyllCMS V1.3.3 Jambase as the default rule set.

Note that you'll find the original Jam README in the file README.ORG
"""

Thoughts?
Jack