ack is released under the [Artistic License 2.0][1].

[1]: https://www.perlfoundation.org/artistic-license-20.html

Artistic License 2.0
====================

Copyright (c) 2000-2006, The Perl Foundation.

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.


Preamble
--------

This license establishes the terms under which a given free software
Package may be copied, modified, distributed, and/or redistributed. The
intent is that the Copyright Holder maintains some artistic control
over the development of that Package while still keeping the Package
available as open source and free software.

You are always permitted to make arrangements wholly outside of this
license directly with the Copyright Holder of a given Package. If the
terms of this license do not permit the full use that you propose to
make of the Package, you should contact the Copyright Holder and seek
a different licensing arrangement.


Definitions
-----------

"Copyright Holder" means the individual(s) or organization(s) named in
the copyright notice for the entire Package.

"Contributor" means any party that has contributed code or other material
to the Package, in accordance with the Copyright Holder's procedures.

"You" and "your" means any person who would like to copy, distribute,
or modify the Package.

"Package" means the collection of files distributed by the Copyright
Holder, and derivatives of that collection and/or of those files. A given
Package may consist of either the Standard Version, or a Modified Version.

"Distribute" means providing a copy of the Package or making it accessible
to anyone else, or in the case of a company or organization, to others
outside of your company or organization.

"Distributor Fee" means any fee that you charge for Distributing this
Package or providing support for this Package to another party. It does
not mean licensing fees.

"Standard Version" refers to the Package if it has not been modified,
or has been modified only in ways explicitly requested by the Copyright
Holder.

"Modified Version" means the Package, if it has been changed, and such
changes were not explicitly requested by the Copyright Holder.

"Original License" means this Artistic License as Distributed with the
Standard Version of the Package, in its current version or as it may be
modified by The Perl Foundation in the future.

"Source" form means the source code, documentation source, and
configuration files for the Package.

"Compiled" form means the compiled bytecode, object code, binary, or any
other form resulting from mechanical transformation or translation of
the Source form.


Permission for Use and Modification Without Distribution
--------------------------------------------------------

(1) You are permitted to use the Standard Version and create and use
Modified Versions for any purpose without restriction, provided that you
do not Distribute the Modified Version.


Permissions for Redistribution of the Standard Version
------------------------------------------------------

(2) You may Distribute verbatim copies of the Source form of the Standard
Version of this Package in any medium without restriction, either gratis
or for a Distributor Fee, provided that you duplicate all of the original
copyright notices and associated disclaimers. At your discretion, such
verbatim copies may or may not include a Compiled form of the Package.

(3) You may apply any bug fixes, portability changes, and other
modifications made available from the Copyright Holder. The resulting
Package will still be considered the Standard Version, and as such will
be subject to the Original License.  Distribution of Modified Versions
of the Package as Source

(4) You may Distribute your Modified Version as Source (either gratis
or for a Distributor Fee, and with or without a Compiled form of the
Modified Version) provided that you clearly document how it differs
from the Standard Version, including, but not limited to, documenting
any non-standard features, executables, or modules, and provided that
you do at least ONE of the following:

(a) make the Modified Version available to the Copyright Holder of
the Standard Version, under the Original License, so that the Copyright
Holder may include your modifications in the Standard Version.

(b) ensure that installation of your Modified Version does not prevent
the user installing or running the Standard Version. In addition, the
Modified Version must bear a name that is different from the name of
the Standard Version.

(c) allow anyone who receives a copy of the Modified Version to make
the Source form of the Modified Version available to others under (i)
the Original License or (ii) a license that permits the licensee to
freely copy, modify and redistribute the Modified Version using the
same licensing terms that apply to the copy that the licensee received,
and requires that the Source form of the Modified Version, and of any
works derived from it, be made freely available in that license fees
are prohibited but Distributor Fees are allowed.


Distribution of Compiled Forms of the Standard Version or Modified Versions without the Source
----------------------------------------------------------------------------------------------

(5) You may Distribute Compiled forms of the Standard Version without
the Source, provided that you include complete instructions on how to
get the Source of the Standard Version. Such instructions must be valid
at the time of your distribution. If these instructions, at any time
while you are carrying out such distribution, become invalid, you must
provide new instructions on demand or cease further distribution. If
you provide valid instructions or cease distribution within thirty days
after you become aware that the instructions are invalid, then you do
not forfeit any of your rights under this license.

(6) You may Distribute a Modified Version in Compiled form without the
Source, provided that you comply with Section 4 with respect to the
Source of the Modified Version.


Aggregating or Linking the Package
----------------------------------

(7) You may aggregate the Package (either the Standard Version or
Modified Version) with other packages and Distribute the resulting
aggregation provided that you do not charge a licensing fee for the
Package. Distributor Fees are permitted, and licensing fees for other
components in the aggregation are permitted. The terms of this license
apply to the use and Distribution of the Standard or Modified Versions
as included in the aggregation.

(8) You are permitted to link Modified and Standard Versions with other
works, to embed the Package in a larger work of your own, or to build
stand-alone binary or bytecode versions of applications that include the
Package, and Distribute the result without restriction, provided the
result does not expose a direct interface to the Package.


Items That are Not Considered Part of a Modified Version
--------------------------------------------------------

(9) Works (including, but not limited to, modules and scripts) that
merely extend or make use of the Package, do not, by themselves, cause
the Package to be a Modified Version. In addition, such works are not
considered parts of the Package itself, and are not subject to the terms
of this license.


General Provisions
------------------

(10) Any use, modification, and distribution of the Standard or Modified
Versions is governed by this Artistic License. By using, modifying or
distributing the Package, you accept this license. Do not use, modify,
or distribute the Package, if you do not accept this license.

(11) If your Modified Version has been derived from a Modified Version
made by someone other than you, you are nevertheless required to ensure
that your Modified Version complies with the requirements of this license.

(12) This license does not grant you the right to use any trademark,
service mark, tradename, or logo of the Copyright Holder.

(13) This license includes the non-exclusive, worldwide, free-of-charge
patent license to make, have made, use, offer to sell, sell, import
and otherwise transfer the Package with respect to any patent claims
licensable by the Copyright Holder that are necessarily infringed by the
Package. If you institute patent litigation (including a cross-claim or
counterclaim) against any party alleging that the Package constitutes
direct or contributory patent infringement, then this Artistic License
to you shall terminate on the date that such litigation is filed.

(14) Disclaimer of Warranty: THE PACKAGE IS PROVIDED BY THE COPYRIGHT
HOLDER AND CONTRIBUTORS "AS IS' AND WITHOUT ANY EXPRESS OR IMPLIED
WARRANTIES. THE IMPLIED WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
PARTICULAR PURPOSE, OR NON-INFRINGEMENT ARE DISCLAIMED TO THE EXTENT
PERMITTED BY YOUR LOCAL LAW. UNLESS REQUIRED BY LAW, NO COPYRIGHT HOLDER
OR CONTRIBUTOR WILL BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, OR
CONSEQUENTIAL DAMAGES ARISING IN ANY WAY OUT OF THE USE OF THE PACKAGE,
EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.