.. _licensing2:

=======
License
=======

| CVX: A system for disciplined convex programming   
| © 2012 CVX Research, Inc., Austin, TX.
| http://cvxr.com
| info@cvxr.com

Thank you for using CVX!

The files contained in the CVX distribution come from several different
sources and are covered under a variety of licenses. Those files owned by CVX
Research, Inc. are released under one of two licenses: the *CVX Standard 
License* and the *CVX Professional License*. The CVX Professional License
is not a permissive license, and it does not permit redistribution. The
CVX Standard License, on the other hand, is in fact the GNU Standard
License, Version 3, amended with a single additional permission.

CVX Professional License
------------------------

The full CVX package, including the commercial solver functionality,
includes several files in Matlab *p-code* format. This format contains
an encrypted form of Matlab bytecode, and are distinguished by a ``.p``
suffix. For instance, the package currently includes the files

::

    shims/cvx_mosek.p
    shims/cvx_gurobi.p
    cvx_license.p

but future versions may add additional .p files, and they are governed
by this text as well. Furthermore, all files within the subdirectories

::

    gurobi/
    mosek/  

are licensed by Gurobi Optimization and MOSEK ApS, respectively, for
inclusion in the CVX package by contractual agreement. In the future,
CVX Research may include other commercial solvers in its distributions,
and they will be governed by this section as well.

Any package containing even one of the files mentioned above is subject
to the *CVX Professional License*. You may *not* redistribute such a package,
nor make it available on a public repository, without the express written
consent of CVX Research, Inc. Of course, the full CVX package is freely
available to download directly from our servers, so please feel free to
refer people to our web site---even directly to our 
`download page <http://cvxr.com/cvx/download>`_.

CVX Standard License
--------------------

CVX also offers what we call "redistributable" packages that omit all of 
the files listed above. This package retains all of the functionality of 
CVX, with the exception of its ability to connect to commercial solvers.
Redistributable packages are offered on the same download page as our
standard packages.

The redistributable package is covered by the *CVX Standard License*. This
license is nothing more than the GNU Standard License, Version 3 (GPLv3),
with one additional permission we call the "Free Solver Clause", discused
in the next section.

The full text of the GPLv3 is given in the file GPL.txt found in the top
directory of the CVX package. Please see Section 7 of this license for more
information about additional permissions such as the one offered here. In
particular, you are free to *remove* this permission from any modified 
version of CVX you create; but you may not *create new ones*. 

You must include the files LICENSE.txt and GPL.txt in unmodified form when
redistributing this software or any subset of it. If you did not receive a
copy of either of these files with your distribution, please contact us.

The Free Solver Clause
----------------------

We have chosen to add a single "additional permission" clause to the CVX
Standard License above and beyond the text of the GPLv3. This full text of 
this clause is contained in the following paragraph:

    You are free to modify CVX to connect to any solver whose full
    functionality is provided free of charge to *all* users, even if the 
    solver's license is otherwise incompatible with the GNU Standard 
    License Version 3. This permission does not apply to solvers which 
    are free just to certain users (e.g., academic users), free for 
    limited time periods, or free with restricted functionality.

CVX relies upon other software packages, called *solvers*, to perform many 
of its underlying calculations. Currently CVX supports free solvers SeDuMi
and SDPT3, and commercial solvers Gurobi and MOSEK. The resulting nexus of 
free and commercial software presents a licensing challenge. Our vision is
guided by three goals:

- to ensure that CVX remains fully free to use with any fully free solver.
- to support the development and support of CVX by selling interfaces to 
  commercial solvers to commercial customers.
- to provide the academic community with our full commercial capabilities
  at no charge. (Obviously this depends upon the cooperation of commercial
  solver vendors. Gurobi and MOSEK fully support this goal.)

The terms we lay out here are intended to support these trifold goals.  

We invite our users to create new interfaces between CVX and other free
solvers. By  "free", we mean that the solver must be made available at no
charge for to *all* users, including commercial users, without restriction.
Please contact us if you are interested in creating such an interface; we can
offer assistance. If you do create one, please consider submitting it to us
for inclusion in the standard CVX distribution; but you are under no 
obligation to do this. Instead, you can ship the interface code with the
solver itself; or you can construct a modified version of the 
redistributable CVX package with your interface included.

We do not permit the creation and distribution of new interfaces between CVX
and *non-free* solvers---even if those solvers are made available to academic
academic users at no charge. If you are a vendor or developer of a 
commercial solver, and would like to develop or offer a CVX interface to
your users, please contact us at info@cvxr.com. We welcome the opportunity
to support a wider variety of commercial solvers with CVX, and are willing
to devote engineering resources to make those connections. Of course, we 
hope that you support our goal of making commercial solver capability
available at no charge to academic customers; and our licensing interface
helps to facilitate that offering.

If you are a user of a particular commercial solver and would like to see it
supported by CVX, please contact your solver vendor---but please contact us
at info@cvxr.com as well. If there is sufficient demand, and it proves
technically and financially feasible, we will reach out to the solver vendor
to work on an implementation.

Bundled solvers
----------------

The solvers SDPT3, SeDuMi, Gurobi, and MOSEK are distributed with CVX in the 
``sdpt3/``, ``sedumi/``, ``gurobi/``, and ``mosek/`` subdirectories, respectively. (The
redistributable version of CVX does not include ``gurobi/`` and ``mosek/``.) Future
versions of CVX may include additional solvers as well, each in their own 
subdirectories. None of these packages are owned by CVX Research, Inc. They 
are included with permission of the authors. The solvers SDPT3 and SeDuMi
are subject to the terms of the GPLv2; therefore, you are free to redistribute
them under the terms of that license.

Example library
---------------

The contents of the example library, which is distributed with CVX in the
examples/ subdirectory, is *public domain*. You are free to use them in any
way you wish; but when you do, we request that you give appropriate credit
to the authors. A number of people have contributed to the examples in this
library, including Lieven Vandenberghe, Joëlle Skaf, Argyris Zymnis, Almir
Mutapcic, Michael Grant, and Stephen Boyd. If you would like to offer some
examples to be included in this library, and are willing to release them to
the public domain, please contact us!

No Warranty
-----------

This program 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.
