Unzip utility choice decision

[Matthew Seaman]

On 25/12/2015 08:58, Dangling Pointer wrote:

>> The answer is of course for the more permissive license.

> Is it? This is exactly what I have asked in first post: What is the
> point of having another unzip utility with lesser implementation and
> options, when we already have one. Is it because of license
> differences? Yes/No (preferably in a non-sarcastic manner..) I am not
> sure about the answer, that is why I am asking.

Hmmm... except that the version of zip used by (most) Linux distros
seems to be the one provided by Info-Zip, and that nowadays has a
reasonably permissive license:

http://www.info-zip.org/pub/infozip/license.html

The first two clauses are pretty much standard BSD licence; it's just
the 3rd and 4th clauses protecting various names used by Info-Zip that
are different.  (Something that's normally handled separately by
registering appropriate trademarks.  Curious...)

The reason for the difference between the various unzip programs is that
the base system unzip(1) is built around libarchive -- see
http://www.libarchive.org/ -- which also provides the BSD licensed
versions of a number of other commands including tar(1) and cpio(1).  So
you can just point tar at a zip archive or a .iso image and list the
contents or extract files, which is pretty handy.  However libarchive
doesn't provide the ability to write to a zip archive, and there are
some newer zip formats it can't cope with at all.  IIRC, you need the
ports version of zip(1l)/unzip(1L) to handle zip64 format archives.

So, while the answer /is/ about using a more permissive license, it's
actually more to do with the licensing of tar(1) and cpio(1) where the
alternatives are under the GPL -- unzip(1) is just there as a side
effect, because it costs almost nothing to provide it.

	Cheers,

	Matthew


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