European Union Public Licence

The European Union Public Licence (EUPL) is a free software licence that has been created and approved by the European Commission. The licence is available in 23 official languages of the European Union. All linguistic versions have the same validity. Its latest version, EUPL v1.2, was published in May 2017.
Software, mainly produced by European administrations, has been licensed under the EUPL since the launch of the European Open Source Observatory and Repository (OSOR) in October 2008, now part of Joinup collaborative platform.
History.
EUPL was originally intended to be used for the distribution of software developed in the framework of the IDABC programme, given its generic scope it was also suitable for use by any software developer. Its main goal is its focusing on being consistent with the copyright law in the Member States of the European Union, while retaining compatibility with popular free software licences such as the GNU General Public License. The first IDABC software packages mentioned are CIRCA groupware, IPM and the eLink G2G, G2C, G2B specification software.
Comparison to other open source/free software licences.
EUPL is the first open source licence to be released by an international governing body. A goal of this licence is to create an open-source licence available into 23 official languages of the European Union, and that is sure to conform to the existing copyright laws of the Member States of the European Union.
The licence was developed with other open-source licences in mind and specifically authorizes covered works to be re-released under the following licences, when combined with their covered code in larger works:
Many other OSI-approved licences are compatible with the EUPL: JOINUP publish a general compatibility matrix between all OSI-approved licences and the EUPL.
An overview of the EUPL licence and on what makes it different has been published in OSS-Watch.
In 2020, the European Commission publishes its Joinup Licensing Assistant, which makes possible the selection and comparison of more than 50 licences, with access to their SPDX identifier and full text.
Versions.
EUPL v1.0 was approved on 9 January 2007. 
EUPL v1.1 was approved by the European Commission on 9 January 2009. EUPL v1.1 is OSI certified as from March 2009.
EUPL v1.2 was published in May 2017. EUPL v1.2 is OSI certified in July 2017.
Version 1.2.
The EUPL v1.2 was prepared as from June 2013 its decision process started in 2016 and released on 19 May 2017. A principal objective of the EUPL v1.2 is to update the appendix of compatible licences to cover newer popular licences such as the GNU GPLv3 and AGPLv3. 
According to the EUPL v.1.1, the European Commission may publish other linguistic versions and/or new versions of the EUPL, so far this is required and reasonable, without reducing the scope of the rights granted by the Licence. Future upgrades will not be applicable automatically when software was expressly released "under the EUPL v.1.1 only".
New provisions cover the Application service provider loophole of software distribution: Distribution and/or Communication (of software) includes providing on-line "access to its essential functionalities".
A specificity of the EUPL v1.2 is that, at the contrary of the GPL, it is compatible with all other reciprocal licenses listed in the EUPL appendix. Compatibility means that after merging the covered code with code covered by a compatible license, the resulting (combined) derivative work can be distributed under the compatible license. 
Another specificity of the EUPL is that it is interoperable, without any viral effect in case of static and dynamic linking. This currently depends on European and national law, according to the Computer Programs Directive (Directive 91/250 EEC or 2009/24). Recital 10 of this Directive defines interoperability and recital 15 states that for making two programs interoperable, the code needed can be copied, translated or adapted. For example take program A (new original code just written) and program B (a program licensed by a third party), the developer/licensor of A, who is also a legitimate holder or recipient of B may reproduce in A the needed code from B (e.g. the APIs or the needed data structures from program B) without copyright infringement and without authorization from the copyright holder of B. The licensor of A can do and distribute this without being bonded by conditions or limitations imposed by a licence of program B. This must stay compatible with the normal use of program B and cannot prejudice the legitimate interest of the copyright holder of B. 
Unlike the "articles", the directive "recitals" are not transposed as such in national laws. However, recitals are part of European law: they are serving for understanding the scope and rationale of the law, and will be used by the court for interpreting the law, as the case may be. While recitals in EU Directives and Regulations are not considered to have independent legal value, they can expand an ambiguous provision's scope. They cannot restrict an unambiguous provision's scope, but they can be used to determine the nature of a provision, or to adapt it to new circumstances. For this reason, the German lawyer Niklas Plutte created for the EUPL the new category of "Interoperable copyleft licence".
Member states policies.
As from 2010, EU member states adopt or revise policies aimed to encourage – when appropriate – the open source distribution of public sector applications. The EUPL is formally mentioned in some of these policies: