GNU General Public Licence (GPL | GNU GPL)

In view of the great commercial importance of open source software (OOS), all those who are involved in the software industry would do well to have at least a basic understanding of the relevant licence conditions. With this in mind, we have put together a brief overview of the structure of one of the most commonly used open source licences, the GNU General Public Licence (GPL | GNU GPL).

The GNU General Public Licence belongs to the category of strong copyleft licences. The user of open source software licenced under a GNU General Public Licence is permitted to reproduce the work or derivative works, provided those reproductions or works are also made subject to the GNU GPL licence conditions. The aim of such a licence is to secure the free use of reproductions and works derived from the original open source code.

Developers of GPL software can currently choose between version 2 (GPL v2) and version 3 (GPL v3) of the GNU General Public Licence. Under the latter licence version, developers are permitted to request payment of a royalty when distributing a copy of the developed software, provided the remaining licence conditions are adhered to and the software remains open source.

Users’ rights

Under the GNU GPL, licensed software can be used and reproduced by anyone and for any purpose, including for commercial purposes and use as component parts in proprietary software.

Due to the open source feature, software developers can examine the original source code and freely make modifications and further develop the software. Both the original software and derivate works can be reproduced and made available not only on data storage media but also via the internet. The new software products can also be distributed through Application Service Providing (ASP) or Software as a Service (SaaS).

Users’ duties

To reflect the wide ranging usage rights granted by GNU General Public Licences, there are a number of duties that licensees must fulfil. Here it should be distinguished between the distribution of modified and unmodified software.

When distributing the original open source software it is necessary to include a reference to the copyright holder, a full copy of the licence text and a note excluding liability for warranty (known as “acquisition as is”).

In addition, regardless of the form of distribution, the user is required to include the source code and to make it publicly.

Also, where modified versions of the original open source software are to be distributed, it is important to include reference to the date the modifications were made, so that all who use the software are aware.

It is also important to remember that the partially or wholly derived versions of the GPL software must be made subject to conditions of the GNU General Public Licence (grant back clause).

Viral effect of open source hybrids

The GNU GPL licence can lead to problems for software developers and software companies.

For example, a company that uses open source components to help develop commercial software products may find that the newly developed software is subject to the copyleft effect. This could lead to the derivative software and its code, which may have been developed following the expenditure of much time, effort and money, having to be made available under an open source licence. Consequently, the developed software may become commercially unusable.

Nevertheless, GNU GPL does not subject every kind of software modification to copyleft. Indeed, it is possible to place a newly developed product under a proprietary licence, and therefore allow for commercial exploitation, provided the commercial and open source elements can be distributed distinct from one another. In this case, no derivative work is made. The requirement is that there is a separate and independent work. This can be determined on the individual circumstances.

It is therefore highly advisable to seek legal assistance when planning to develop software which mixes proprietary and GPL software. This will enable a legal evaluation to be undertaken on the risk in terms of marketability. In some cases, it may be useful to make use of a GNU Lesser General Public Licence (GNU LGPL).

Other problem areas

Despite the German courts having generally recognised GNU General Public Licences, their strong reliance on US American copyright law gives rise to a number of problems.

For example, the fact that under the GNU GPL users can distribute open source software or their derivatives in Germany leads to a sort of liability loophole, as under the open source licence conditions liability for the software or derivative is excluded. This situation clashes with German copyright law which classifies software licences as standard terms and conditions. Under German law, a standard term clause fully excluding liability to third parties is invalid, even if the new product is distributed free of charge.

Avoiding complications

To avoid licensing complications when utilising open source software for product development, it is highly advisable to seek expert legal advice.


Do you have questions about IT law, licences or data protection? We are happy to help!
German lawyer, Christian Solmecke, and his expert team are available to answer your questions.
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Christian Solmecke is a partner at the law firm WILDE BEUGER SOLMECKE. He is the author of numerous legal publications in the area of internet and IT law. He is also an associate lecturer for social media law at the Cologne University of Applied Sciences.

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