Licences for open source software

What is open source software?

Open source software is software which is freely distributed under the Open Source Initiative’s licensing requirements.  Many people now write software and are happy to let others use it, modify it or copy it at no charge.  Distribution is controlled under licence, two of the most popular being the GNU General Public Licence and the Mozilla Public Licence.  But although open source software is distributed without charge it is still protected by copyright law, and the author’s and the owner’s rights are still fully protected.  Nevertheless, if a person who owns the copyright in software wants to allow others to us it free of charge, or to modify it, then a number of legal issues may arise.  For example, a person may obtain open source software at no charge, modify it, and then distribute for a fee.  Alternatively, a person who modifies open source software may then become liable for defects or if third party intellectual property rights are infringed.  Some of the issues pertaining to open source software are discussed below.


A copyright notice should be provided on the software, using the standard © symbol and giving the author’s name and the year of first publication.  If the software can be modified and redistributed then the relevant copyright notices should also be attached.  A person who modifies the software without permission will be liable under s296ZG of the Copyright, Designs and Patents Act 1988 as if they had infringed the copyright


Some patents for software do exist even though s1(2) of the Patents Act 1977 states that computer programs cannot be inventions for the purposes of the Act.  Although it is possible that a person may modify software and then obtain a patent for it, previous versions of the software may still be used and will not breach the patent.  Subsequent versions, however, may breach the patent, though this goes against the general spirit of open source software being available to all.  One solution is to require that modified software be subject to free and non-exclusive licences, allowing further use and development. 


Both the source code (the original text statements input by the programmer using a programming language) and the object code (the sequence of instructions given to a computer after the source code has been compiled using a program compiler) should be made available with the software, along with any other materials concerning development and testing.  It is common for these additional materials to be provided for a fee, as often they are essential for further developing and modifying the software.  Modified versions of the software may be further freely distributed, along with all relevant materials that the developer had advantage of when compiling the new version.

Liability for defects

It is common for software to contain errors.  If serious enough, these errors could cause substantial loss or damage to the user or a third party.  Consequently, open source software licences usually exclude, as far as legally possible, warranties regarding fitness for purpose, quality, freedom from defects, and so on.  Excluding liability in this way is possible, but only if it is reasonable in the circumstances.  A licensee who modifies and distributes software should include a term in the new licence that the original developers accept no liability regarding the software (except for death or personal injury) and make no warranties for it. 

Third party rights

There is a risk that software will infringe third party rights such as copyright.  Consequently, licences for open source software should contain provisions in this regard, such as a clause that all effort has been taken to ensure third party rights have not been infringed, though this is somewhat weak and unsatisfactory. Trademarks, images and logos should not be the same or similar to registered, or even unregistered, trademarks.  As far as patents and design rights are concerned, great care must be taken to ensure that these are not infringed, as these rights can be infringed without having any knowledge of the subject matter of them.