License — CVX Users' Guide

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# 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.

## 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.

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