OpenFOAM is Open Source

The following article was written on 11th February 2011 to present OpenCFD’s views on OpenFOAM and open source software. Later in 2011, OpenCFD established the OpenFOAM Foundation and transferred the copyright of the OpenFOAM source code to it, to ensure that OpenFOAM is licensed free and open source only as expressed in this article.

OpenCFD released OpenFOAM as free, open source software, licensed under the GNU General Public Licence (GPL), in December 2004. Since then, its popularity has grown rapidly, largely as a consequence of it being open source. OpenCFD has developed OpenFOAM — adding half a million lines of code in 6 years — through funding from companies and other organisations. We always insist the developments we do are released free and open source under the GPL, so that OpenFOAM moves forward with useful, new functionality becoming available with each release.

In most cases, companies are immediately willing to fund developments that they know will become open source because they appreciate that they are already gaining from the free availability of the current code that has been funded by others and are happy to “give something back”. Some companies require more persuasion and a few require stronger campaigning on our behalf, but the developments we make are inevitably released under the GPL.

If OpenFOAM was not free and open source, companies would not invest in the development of OpenFOAM under the same conditions. Its development would stagnate which is not in the interests of the users. People have committed to OpenFOAM on the understanding that it is free, open source software that is continually being developed and improved; people also specifically choose this form of software because they agree with the underlying philosophy and/or in its reputation for versatility and reliability. They all have our assurance that the situation will not change: we will release OpenFOAM always (and only) free and open source.

We are often contacted by people who present us with a proposal to release OpenFOAM under a separate, non-free proprietary licence. [Note: The OpenFOAM Foundation now licenses OpenFOAM, not OpenCFD (see introduction).] These people invariably begin by saying “we love open source and what you are doing with OpenFOAM”. Only later they ask “have you considered dual licensing?” before finally asking for a separate licence. The answer is always “no” and it will always be “no”.

There may be others who directly seek to bypass the terms of the GPL. They ignore the fact that the people involved in the development of OpenFOAM, do so on the understanding that their work is released free and open source under the GPL. It is their work and they make a conscious decision to release it for free. No-one else has that right, and no-one else has the right to use that software other than under the terms of the GPL — which ensures freedom for all.

Our belief in free, open source software goes beyond our promise to the OpenFOAM users. Primarily, we think people should have a right to modify and redistribute software they use and that they should have a guarantee that they will be able to use it indefinitely; free, open source software, gives them this. We believe in open file formats; we oppose software patents; and, we do not work on operating systems that limit people’s freedom to use computers and software the way they want to.

So, to avoid any doubt: OpenCFD will always release OpenFOAM as free, open source software under the GPL or one of its derivatives, such as the Affero GPL. It will never be released under weaker licences that allow exploitation by producers of non-free software, such as the Lesser GPL which the Free Software Foundation does not generally recommend. As they put it, the producers of non-free software “will try to convince authors not to contribute libraries to the GPL-covered collection… promising ‘more users for this library’.” They conclude by saying: “We free software developers should support one another. By releasing libraries that are limited to free software only, we can help each other’s free software packages outdo the proprietary alternatives. The whole free software movement will have more popularity, because free software as a whole will stack up better against the competition.”

OpenCFD supports this view and will do everything it can to ensure OpenFOAM remains free and open source only and is not included in any non-free, proprietary software products.