ESA Open Source Policy

Open Source Software (OSS) is computer software recognised by the Open Source Initiative (OSI), whose source code is made available under a copyright licence that allows users to use, study, change, and improve the software, and to redistribute it in a modified or unmodified form.

The use of OSS world-wide has increased significantly in the last decade to the point that OSS plays today an essential role in all industrial sectors and government, including space and defence.

This trend is due to the generally perceived benefits of OSS, namely:

ESA could not remain oblivious to this trend: in the last two decades, ESA, like any other relevant organisation using and procuring software, has increasingly been making use of OSS. Since 2004, the General Clauses and Conditions for ESA contracts, ESA/REG/002, rev. 2 (“GCC”)[1] (sub-clauses 42.10 and 42.11) foresee the possibility of open source licensing of software developed under ESA contracts.

In addition, not least due to industrial commercial interests, ESA had to implement an effective OSS strategy that opens the necessary opportunities for industry in a global market, inside and outside of the space sector. A clear strategy on OSS consolidates the leadership of ESA in software developments for the space sector and allows ESA to fulfill its mandate as a focal point for European research and innovation.

Considering the risks and potential consequences associated with the distribution of the OSS for ESA, it is of the utmost importance that the ESA Software Licensing Board authorisation is granted and recorded in a Software Licensing Authorisation (SWLA) prior to any distribution of any software outside ESA.


Distribution of Open Source Software within the ESA Member States[2]

When there is no need/added value to implement a world-wide OSS scheme, an “ESA Community Software” licensing regime can be implemented. In this case use, modification and further licensing of the software shall be restricted to individuals or entities belonging to the ESA Member States.

This software is defined as software licensed according to the main principles of Open Source, with the major exception of the Licensed Territory being limited to the ESA Member States. This limitation makes this type of licensing incompatible with the commonly accepted definition of Open Source given by the Open Source Initiative[3], which requires unrestricted distribution.

Such software would therefore benefit from the OSS philosophy while remaining within the ESA environment and should be made available as part of the European Space Software Repository[4].


Distribution of Open Source Software outside the ESA Member States

This scheme is generally suitable for the application cases described as software supporting the implementation of open standards or the processing of mission data.

For developments initiated by ESA, not subject to pre-existing licensing constraints, ESA’s own OSS licence template shall be revised, ensuring compatibility with the ESA internal procedures and licensing standards. In particular, the Industrial Policy Committee (IPC) approval is required prior to any distribution of an ESA owned software outside of the ESA Member States.

In case pre-existing, non-ESA, OSS is adopted as a basis for ESA procurements, the licensing regime for the derived work would by definition be the one applicable to the existing product itself. Since certain OSS licences are not compatible with the ESA rules or may inflict unwanted constraints, any proposal for re-using existing OSS shall be checked against a list of acceptable OSS licences.

For the cases entailing world-wide distribution (“proper” OSS), the main possible cases are the following ones:



(licensing framework is inherited),



(licensing framework is inherited)



(licensing framework imposed by ESA)


Scenario 1


Collaboration with Universities and Research Institutes

This case refers to software developments under ESA contracts that are contributions to scientific initiatives based on sharing of software under an Open Source scheme. It covers also the development of advanced software applications in collaboration with Universities and Research Institutes. ESA as a research organisation has a general interest in collaborating in R&D with Universities and Research Institutes located within and outside ESA's Members States and share the results. Such collaboration scheme requires the exchange of the generated software and libraries within the software development community.

Scenario 2


Promotion of space international standards


OSS can effectively be used to promote the widest possible use of open standards whose implementation and adoption is facilitated by supporting software development kits and applications. In many instances, this is in the interest of European space activities and reinforces competitiveness of European industry world-wide. Distribution of such software under an OSS licence helps in promoting the wide adoption and use of international space related standards.

Scenario 3


Mission Data Processing tools

Sharing knowledge between ESA and its partners is essential for the mission success, as it is the case for mission data processing software, where ESA, other participating agencies, European institutions (EU, CERN, ESO, etc.) and education centres (University, schools, etc.), the science community, payload providers and industry involved in the procurement of the space system need to cooperate tightly together.

Scenario 4


Engineering Tools

Specialised engineering analysis tools, for which only a very limited user community exists, and collaboration between the users to share the maintenance and upgrade of the tool is beneficial on a world-wide basis.

Scenario 5


Industrial Commercial Interest


OSS model is beneficial to industry e.g. for promotion purposes or for economical and quality reasons (engaging a large user base to test and improve a product). Some companies are interested to release their in-house software as open source software to reduce maintenance cost since the open source community built around the product participates in the software validation and improvement. Some companies expect lucrative service contracts if their software gets into the market by being free and available in source code.




Assignment of Intellectual Property Rights

OSS procurements can be applied within ESA in compliance with the principles set forth by the ESA Convention, the Rules concerning Information, Data and Intellectual Property, GCC and other internal procedures.

In general, OSS procurements can be implemented with the developer(s) of the software (original and derived products) retaining the IP. In certain cases, however, ESA might request the assignment of the IP according to the Open Source Clause 42.10 of the GCC, e.g. when no industrial leader can be identified.


ESA Open Source Software Repository

An OSS repository has been setup with the following purpose:


This repository provides European space actors with information on OSS products for space, and associated licensing and legal aspects. It also supports the assessment of the maturity and verification status of OSS products, thereby facilitating the pre-selection of OSS products and services. The repository also features community forums to support collaborative efforts involving software developers and end-users.

The OSS repository helps to control the licensing of such software by ESA in a more centralized way in order to minimize risks of possible infringements. It also allows industry to have visibility of ESA and other European developments and contribute to the fulfilment of ESA’s mandate to spur European cooperation.


General Principles for selecting the OSS Model in ESA

The application of the OSS to ESA software developments shall be in line with the achievement of the following goals:

  1. Maximise the efficiency in the procurement of software products for application in space programmes, i.e. saving costs and increase quality and innovation
  2. Avoid excessive dependency on software suppliers where this poses a risk for the implementation of ESA programmes, i.e. avoiding lock-in situations
  3. Minimise duplication of efforts in Europe, where no other benefit is achieved as per ESA Convention
  4. Stimulate competition for proprietary software on the basis of innovation and added value features for the customer, rather than on standard features, for which a reliable and affordable supply already exists
  5. Maximise the return on investment of software developments for the European space community at large, by providing, where appropriate, OSS alternative products in addition to supporting proprietary software products
  6. Maximise the benefits from using already existing software available under an Open Source licence, as long as the licence conditions are acceptable and do not pose unnecessary risks for ESA, also in view of further licensing to third parties of the final products
  7. Maximise the re-use of software products from mission to mission, where this leads to concrete savings and has no other draw-backs
  8. Contribute to scientific initiatives based on sharing of OSS, where such contribution is in the interest of ESA and its Member States
  9. Promote the widest possible use of standards, in particular those developed in partnership with industry and National agencies e.g. in the frame of ECSS, CCSDS, and whose adoption is essential for the efficiency of European space projects
  10. Improve the quality of software products of interest for the European space sector by means of collective efforts as the ones typical for OSS communities
  11. Open up market opportunities for European space industry in other industrial sectors
  12. Help start-up companies and small and medium sized enterprises to establish themselves as software and service providers, where it is suitable for stimulating innovation
  13. The OSS model is not meant to constitute the default option for software development under ESA contracts, but shall be considered for the application scenarios described above
  14. ESA shall support the dissemination of information on existing OSS products applicable to space and the OSS repository shall support this objective
  15. The application of the OSS scheme shall remain in line with the spirit of the GCC regarding the treatment of IP
  16. Where no industrial leader can be identified, ESA can act as the agency coordinating the OSS community leaving space for industrial business cases to develop through OSS related maintenance and support services. In this case transfer of OSS IP to ESA can be implemented
  17. In line with ESA’s mandate, the legitimate commercial interests of industry shall be respected
  18. The procurement and use of OSS shall follow the quality standards and rules applicable for software reuse

Selection of the ESA Licence

The choice (or obligation) for a distributor to use a given type of OSS licence depends on whether existing software is re-used for the development and what constraints, if any, are imposed by the relative licensing conditions. Reflecting the characteristics of the various mainstream OSS licences, the ESA licences have been developed such that it can be configured to be:


Reciprocal / Strong “Copyleft”

Minimum or no freedom, for a downstream distributor, to use different licensing terms than the initial licence for the original software or a modified version (the “Derived Works”).

Reciprocal / Weak “Copyleft”

The definition of “Derived Works” is less encompassing, thus eliminating the possible spill-over of the Copyleft conditions onto other software developed using the original software but considered as distinct (“Lesser” or “Library-type” licences, like LGPL);

Permissive / “Non-Copyleft”

Essentially, the constraints imposed on downstream distributors are drastically reduced and it is possible to distribute “Derived Works” under different, even “Closed-Source” / “Proprietary”, licensing regimes.


Esa accommodates the above copyleft options through three different types of the ESA Public Licence (ESA-PL). The ESA-PL entails world-wide licensing in accordance with the basic principles of OSS.  However, in order to cater for situations where licensing is to be limited to the territory of the ESA Member States, ESA has developed the so-called ESA Software Community License (ESCL) which, although not qualifying as a proper OSS licence, implements the OSS principles to the maximum extent.  The ESCL accommodates the same copyleft options as the ESA-PL.


The applicable versions of the above ESA licences are available under, and reflect the above copyleft options as follows:



OSS-like distribution within ESA Member States

OSS-like distribution outside ESA Member States

Reciprocal / Strong “Copyleft”

ESA Community Licence – Strong Copyleft (Type 1)

ESA Public Licence – Strong Copyleft (Type 1)

Reciprocal / Weak “Copyleft”

ESA Community Licence – Weak Copyleft (Type 2)

ESA Public Licence – Weak Copyleft (Type 2)

Permissive / “Non-Copyleft”

ESA Community Licence – Permissive (Type 3)

ESA Public Licence –Permissive (Type 3)



[1] Available at: under "Reference Documentation" ---> "Administrative Documents".

[2] As of August 2017 the Member States are Austria, Belgium, Czech Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Ireland, Italy, Luxembourg, The Netherlands, Norway, Poland, Portugal, Romania, Spain, Sweden, Switzerland and the United Kingdom.