Valid‐License‐Identifier: LGPL‐2.1 Valid‐License‐Identifier:
LGPL‐2.1+ SPDX‐URL: https://spdx.org/licenses/LGPL‐2.1.html
To use this license in source code, put one of the following
tag/value pairs into a comment according to the placement
guidelines in the licensing rules documentation.
For ’GNU Lesser General Public License (LGPL) version 2.1 only’
For ’GNU Lesser General Public License (LGPL) version 2.1 or
SPDX‐License‐Identifier: LGPL‐2.1+ License‐Text:
GNU LESSER GENERAL PUBLIC LICENSE Version 2.1, February 1999
Copyright (C) 1991, 1999 Free Software Foundation, Inc. 51
Franklin Street, Fifth Floor, Boston, MA 02110‐1301 USA
Everyone is permitted to copy and distribute verbatim copies of
this license document, but changing it is not allowed.
[This is the first released version of the Lesser GPL. It also
counts as the successor of the GNU Library Public License,
version 2, hence the version number 2.1.]
The licenses for most software are designed to take away your
freedom to share and change it. By contrast, the GNU General
Public Licenses are intended to guarantee your freedom to share
and change free software‐‐to make sure the software is free for
all its users.
This license, the Lesser General Public License, applies to some
specially designated software packages‐‐typically libraries‐‐of
the Free Software Foundation and other authors who decide to use
it. You can use it too, but we suggest you first think carefully
about whether this license or the ordinary General Public License
is the better strategy to use in any particular case, based on
the explanations below.
When we speak of free software, we are referring to freedom of
use, not price. Our General Public Licenses are designed to make
sure that you have the freedom to distribute copies of free
software (and charge for this service if you wish); that you
receive source code or can get it if you want it; that you can
change the software and use pieces of it in new free programs;
and that you are informed that you can do these things.
To protect your rights, we need to make restrictions that forbid
distributors to deny you these rights or to ask you to surrender
these rights. These restrictions translate to certain
responsibilities for you if you distribute copies of the library
or if you modify it.
For example, if you distribute copies of the library, whether
gratis or for a fee, you must give the recipients all the rights
that we gave you. You must make sure that they, too, receive or
can get the source code. If you link other code with the library,
you must provide complete object files to the recipients, so that
they can relink them with the library after making changes to the
library and recompiling it. And you must show them these terms so
they know their rights.
We protect your rights with a two‐step method: (1) we copyright
the library, and (2) we offer you this license, which gives you
legal permission to copy, distribute and/or modify the library.
To protect each distributor, we want to make it very clear that
there is no warranty for the free library. Also, if the library
is modified by someone else and passed on, the recipients should
know that what they have is not the original version, so that the
original author’s reputation will not be affected by problems
that might be introduced by others.
Finally, software patents pose a constant threat to the existence
of any free program. We wish to make sure that a company cannot
effectively restrict the users of a free program by obtaining a
restrictive license from a patent holder. Therefore, we insist
that any patent license obtained for a version of the library
must be consistent with the full freedom of use specified in this
Most GNU software, including some libraries, is covered by the
ordinary GNU General Public License. This license, the GNU Lesser
General Public License, applies to certain designated libraries,
and is quite different from the ordinary General Public License.
We use this license for certain libraries in order to permit
linking those libraries into non‐free programs.
When a program is linked with a library, whether statically or
using a shared library, the combination of the two is legally
speaking a combined work, a derivative of the original library.
The ordinary General Public License therefore permits such
linking only if the entire combination fits its criteria of
freedom. The Lesser General Public License permits more lax
criteria for linking other code with the library.
We call this license the "Lesser" General Public License because
it does Less to protect the user’s freedom than the ordinary
General Public License. It also provides other free software
developers Less of an advantage over competing non‐free programs.
These disadvantages are the reason we use the ordinary General
Public License for many libraries. However, the Lesser license
provides advantages in certain special circumstances.
For example, on rare occasions, there may be a special need to
encourage the widest possible use of a certain library, so that
it becomes a de‐facto standard. To achieve this, non‐free
programs must be allowed to use the library. A more frequent case
is that a free library does the same job as widely used non‐free
libraries. In this case, there is little to gain by limiting the
free library to free software only, so we use the Lesser General
In other cases, permission to use a particular library in non‐
free programs enables a greater number of people to use a large
body of free software. For example, permission to use the GNU C
Library in non‐free programs enables many more people to use the
whole GNU operating system, as well as its variant, the GNU/Linux
Although the Lesser General Public License is Less protective of
the users’ freedom, it does ensure that the user of a program
that is linked with the Library has the freedom and the
wherewithal to run that program using a modified version of the
The precise terms and conditions for copying, distribution and
modification follow. Pay close attention to the difference
between a "work based on the library" and a "work that uses the
library". The former contains code derived from the library,
whereas the latter must be combined with the library in order to
TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION
0. This License Agreement applies to any software library or
which contains a notice placed by the copyright holder or
authorized party saying it may be distributed under the terms
Lesser General Public License (also called "this License").
licensee is addressed as "you".
A "library" means a collection of software functions and/or
prepared so as to be conveniently linked with application
(which use some of those functions and data) to form
The "Library", below, refers to any such software library or
has been distributed under these terms. A "work based on the
means either the Library or any derivative work under
that is to say, a work containing the Library or a portion of
verbatim or with modifications and/or translated
another language. (Hereinafter, translation is included
limitation in the term "modification".)
"Source code" for a work means the preferred form of the work
modifications to it. For a library, complete source code means
source code for all modules it contains, plus any associated
definition files, plus the scripts used to control compilation
installation of the library.
Activities other than copying, distribution and modification
covered by this License; they are outside its scope. The act
a program using the Library is not restricted, and output
from such a
program is covered only if its contents constitute a work
based on the
Library (independent of the use of the Library in a tool for
it). Whether that is true depends on what the Library does
and what the
program that uses the Library does.
1. You may copy and distribute verbatim copies of the Library’s
source code as you receive it, in any medium, provided that
conspicuously and appropriately publish on each copy an
copyright notice and disclaimer of warranty; keep intact all
that refer to this License and to the absence of any warranty;
distribute a copy of this License along with the Library.
You may charge a fee for the physical act of transferring a
you may at your option offer warranty protection in exchange
for a fee.
2. You may modify your copy or copies of the Library or any
portion of it,
thus forming a work based on the Library, and copy and
modifications or work under the terms of Section 1 above,
you also meet all of these conditions:
a) The modified work must itself be a software library.
b) You must cause the files modified to carry prominent
that you changed the files and the date of any change.
c) You must cause the whole of the work to be licensed at no
all third parties under the terms of this License.
d) If a facility in the modified Library refers to a function
or a table
of data to be supplied by an application program that uses
facility, other than as an argument passed when the
invoked, then you must make a good faith effort to ensure
the event an application does not supply such function or
facility still operates, and performs whatever part of its
(For example, a function in a library to compute square roots
purpose that is entirely well‐defined independent of the
application. Therefore, Subsection 2d requires that any
application‐supplied function or table used by this function
optional: if the application does not supply it, the square
function must still compute square roots.)
These requirements apply to the modified work as a whole. If
identifiable sections of that work are not derived from the
can be reasonably considered independent and separate works in
themselves, then this License, and its terms, do not apply to
sections when you distribute them as separate works. But when
distribute the same sections as part of a whole which is a
work based on
the Library, the distribution of the whole must be on the
terms of this
License, whose permissions for other licensees extend to the
whole, and thus to each and every part regardless of who wrote
Thus, it is not the intent of this section to claim rights or
your rights to work written entirely by you; rather, the
intent is to
exercise the right to control the distribution of derivative
collective works based on the Library.
In addition, mere aggregation of another work not based on the
with the Library (or with a work based on the Library) on a
volume of a
storage or distribution medium does not bring the other work
scope of this License.
3. You may opt to apply the terms of the ordinary GNU General
License instead of this License to a given copy of the
Library. To do
this, you must alter all the notices that refer to this
License, so that
they refer to the ordinary GNU General Public License, version
instead of to this License. (If a newer version than version 2
ordinary GNU General Public License has appeared, then you can
that version instead if you wish.) Do not make any other
change in these
Once this change is made in a given copy, it is irreversible
copy, so the ordinary GNU General Public License applies to
subsequent copies and derivative works made from that copy.
This option is useful when you wish to copy part of the code
Library into a program that is not a library.
4. You may copy and distribute the Library (or a portion or
it, under Section 2) in object code or executable form under
of Sections 1 and 2 above provided that you accompany it with
complete corresponding machine‐readable source code, which
distributed under the terms of Sections 1 and 2 above on a
customarily used for software interchange.
If distribution of object code is made by offering access to
copy from a
designated place, then offering equivalent access to copy the
code from the same place satisfies the requirement to
source code, even though third parties are not compelled to
source along with the object code.
5. A program that contains no derivative of any portion of the
is designed to work with the Library by being compiled or
it, is called a "work that uses the Library". Such a work, in
is not a derivative work of the Library, and therefore falls
scope of this License.
However, linking a "work that uses the Library" with the
an executable that is a derivative of the Library (because it
portions of the Library), rather than a "work that uses the
library". The executable is therefore covered by this License.
states terms for distribution of such executables.
When a "work that uses the Library" uses material from a
that is part of the Library, the object code for the work may
derivative work of the Library even though the source code is
not. Whether this is true is especially significant if the
work can be
linked without the Library, or if the work is itself a
threshold for this to be true is not precisely defined by law.
If such an object file uses only numerical parameters, data
layouts and accessors, and small macros and small inline
lines or less in length), then the use of the object file is
unrestricted, regardless of whether it is legally a derivative
work. (Executables containing this object code plus portions
Library will still fall under Section 6.)
Otherwise, if the work is a derivative of the Library, you may
distribute the object code for the work under the terms of
6. Any executables containing that work also fall under
whether or not they are linked directly with the Library
6. As an exception to the Sections above, you may also combine or
"work that uses the Library" with the Library to produce a
containing portions of the Library, and distribute that work
of your choice, provided that the terms permit modification of
for the customer’s own use and reverse engineering for
You must give prominent notice with each copy of the work that
Library is used in it and that the Library and its use are
this License. You must supply a copy of this License. If the
execution displays copyright notices, you must include the
notice for the Library among them, as well as a reference
user to the copy of this License. Also, you must do one of
a) Accompany the work with the complete corresponding machine‐
source code for the Library including whatever changes were
the work (which must be distributed under Sections 1 and 2
and, if the work is an executable linked with the Library,
complete machine‐readable "work that uses the Library", as
code and/or source code, so that the user can modify the
then relink to produce a modified executable containing the
Library. (It is understood that the user who changes the
definitions files in the Library will not necessarily be
recompile the application to use the modified definitions.)
b) Use a suitable shared library mechanism for linking with
Library. A suitable mechanism is one that (1) uses at run
time a copy
of the library already present on the user’s computer
than copying library functions into the executable, and (2)
operate properly with a modified version of the library, if
installs one, as long as the modified version is interface‐
with the version that the work was made with.
c) Accompany the work with a written offer, valid for at least
years, to give the same user the materials specified in
6a, above, for a charge no more than the cost of performing
d) If distribution of the work is made by offering access to
copy from a
designated place, offer equivalent access to copy the above
materials from the same place.
e) Verify that the user has already received a copy of these
or that you have already sent this user a copy.
For an executable, the required form of the "work that uses
must include any data and utility programs needed for
executable from it. However, as a special exception, the
materials to be
distributed need not include anything that is normally
either source or binary form) with the major components
kernel, and so on) of the operating system on which the
unless that component itself accompanies the executable.
It may happen that this requirement contradicts the license
of other proprietary libraries that do not normally accompany
operating system. Such a contradiction means you cannot use
and the Library together in an executable that you distribute.
7. You may place library facilities that are a work based on the
side‐by‐side in a single library together with other library
not covered by this License, and distribute such a combined
provided that the separate distribution of the work based on
and of the other library facilities is otherwise permitted,
that you do these two things:
a) Accompany the combined library with a copy of the same work
the Library, uncombined with any other library facilities.
be distributed under the terms of the Sections above.
b) Give prominent notice with the combined library of the fact
of it is a work based on the Library, and explaining where
the accompanying uncombined form of the same work.
8. You may not copy, modify, sublicense, link with, or distribute
Library except as expressly provided under this License. Any
otherwise to copy, modify, sublicense, link with, or
Library is void, and will automatically terminate your rights
License. However, parties who have received copies, or rights,
under this License will not have their licenses terminated so
such parties remain in full compliance.
9. You are not required to accept this License, since you have
it. However, nothing else grants you permission to modify or
the Library or its derivative works. These actions are
prohibited by law
if you do not accept this License. Therefore, by modifying or
distributing the Library (or any work based on the Library),
indicate your acceptance of this License to do so, and all its
conditions for copying, distributing or modifying the Library
based on it.
10. Each time you redistribute the Library (or any work based on
Library), the recipient automatically receives a license from
original licensor to copy, distribute, link with or modify
subject to these terms and conditions. You may not impose any
restrictions on the recipients’ exercise of the rights
herein. You are not responsible for enforcing compliance by
parties with this License.
11. If, as a consequence of a court judgment or allegation of
infringement or for any other reason (not limited to patent
conditions are imposed on you (whether by court order,
otherwise) that contradict the conditions of this License,
they do not
excuse you from the conditions of this License. If you cannot
distribute so as to satisfy simultaneously your obligations
License and any other pertinent obligations, then as a
may not distribute the Library at all. For example, if a
would not permit royalty‐free redistribution of the Library
those who receive copies directly or indirectly through you,
only way you could satisfy both it and this License would be
entirely from distribution of the Library.
If any portion of this section is held invalid or
any particular circumstance, the balance of the section is
apply, and the section as a whole is intended to apply in
It is not the purpose of this section to induce you to
patents or other property right claims or to contest validity
such claims; this section has the sole purpose of protecting
integrity of the free software distribution system which is
by public license practices. Many people have made generous
contributions to the wide range of software distributed
system in reliance on consistent application of that system;
it is up
to the author/donor to decide if he or she is willing to
software through any other system and a licensee cannot
This section is intended to make thoroughly clear what is
be a consequence of the rest of this License.
12. If the distribution and/or use of the Library is restricted
countries either by patents or by copyrighted interfaces, the
copyright holder who places the Library under this License
may add an
explicit geographical distribution limitation excluding those
countries, so that distribution is permitted only in or among
not thus excluded. In such case, this License incorporates
limitation as if written in the body of this License.
13. The Free Software Foundation may publish revised and/or new
the Lesser General Public License from time to time. Such new
will be similar in spirit to the present version, but may
detail to address new problems or concerns.
Each version is given a distinguishing version number. If the
specifies a version number of this License which applies to
it and "any
later version", you have the option of following the terms
conditions either of that version or of any later version
the Free Software Foundation. If the Library does not specify
version number, you may choose any version ever published by
14. If you wish to incorporate parts of the Library into other
programs whose distribution conditions are incompatible with
write to the author to ask for permission. For software which
copyrighted by the Free Software Foundation, write to the
Foundation; we sometimes make exceptions for this. Our
decision will be
guided by the two goals of preserving the free status of all
derivatives of our free software and of promoting the sharing
of software generally.
15. BECAUSE THE LIBRARY IS LICENSED FREE OF CHARGE, THERE IS NO
FOR THE LIBRARY, TO THE EXTENT PERMITTED BY APPLICABLE LAW.
OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR
PROVIDE THE LIBRARY "AS IS" WITHOUT WARRANTY OF ANY KIND,
EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE
WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE LIBRARY
YOU. SHOULD THE LIBRARY PROVE DEFECTIVE, YOU ASSUME THE COST
NECESSARY SERVICING, REPAIR OR CORRECTION.
16. IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN
WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY
REDISTRIBUTE THE LIBRARY AS PERMITTED ABOVE, BE LIABLE TO YOU
DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR
DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE
(INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING
INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A
THE LIBRARY TO OPERATE WITH ANY OTHER SOFTWARE), EVEN IF SUCH
OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH
END OF TERMS AND CONDITIONS
How to Apply These Terms to Your New Libraries
If you develop a new library, and you want it to be of the
greatest possible use to the public, we recommend making it free
software that everyone can redistribute and change. You can do so
by permitting redistribution under these terms (or,
alternatively, under the terms of the ordinary General Public
To apply these terms, attach the following notices to the
library. It is safest to attach them to the start of each source
file to most effectively convey the exclusion of warranty; and
each file should have at least the "copyright" line and a pointer
to where the full notice is found.
one line to give the library’s name and an idea of what it does.
Copyright (C) year name of author
This library is free software; you can redistribute it and/or
modify it under the terms of the GNU Lesser General Public
License as published by the Free Software Foundation; either
version 2.1 of the License, or (at your option) any later
This library is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public
License along with this library; if not, write to the Free
Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
Boston, MA 02110‐1301 USA Also add information on how to contact
you by electronic and paper mail.
You should also get your employer (if you work as a programmer)
or your school, if any, to sign a "copyright disclaimer" for the
library, if necessary. Here is a sample; alter the names:
Yoyodyne, Inc., hereby disclaims all copyright interest in the
library ‘Frob’ (a library for tweaking knobs) written by James
signature of Ty Coon, 1 April 1990 Ty Coon, President of Vice
That’s all there is to it!