Eiffel Software Free Eiffel Library License (IFELL)

This license describes the terms applicable to the open-source EiffelBase libraries. For the EiffelStudio and other libraries license terms, please refer to the Eiffel Software end-user license.

On August 4, 1998 -- as part of the Eiffel Summit at TOOLS USA '98 -- Interactive Software Engineering (Eiffel Software) officially made its flagship EiffelBase library available for free to any organization that wants to use it, for either commercial or non-profit purposes.

The terms of the new EiffelBase license are given below. Changes since the original version are recorded in the changes section .

We hope that others will be inspired by this example to release their own reusable Eiffel components to the public.


(This Preamble is not part of the license.)

EiffelBase is one of the principal contributions of Eiffel: a library of fundamental structures and algorithms covering the basics of computing, and resulting from a "Linnaean" effort at a general-purpose taxonomy of computing structures. We believe that EiffelBase is one of the most carefully designed and extensively used libraries in the object-oriented industry. The library and its design principles are described in detail in the book "Reusable Software: The Base Object-Oriented Component Libraries" .

EiffelBase is at the center of Eiffel Software's Eiffel and has been among the major factors attracting users to the technology. In spite of this competitive advantage, Eiffel Software officially announced in June of 1998 that it would release the library to the public in source form, under the terms of the license below. There are two main reasons for this initiative:

  • As the software industry seems poised to adopt the idea of reusable components, we feel that EiffelBase provides an ideal basis and are happy to contribute it to the community.
  • We are impressed by the quality of some public-domain software and the effectiveness of the "open source" movement. We hope that the public availability of EiffelBase in source form will encourage many people to take a close look at the classes of EiffelBase, criticize its weaker points, provide improvements, and add their own high-quality contributions.

About the license

After considering existing license contracts for publicly available software, we felt that the GPL (Gnu Public License) as well as LGPL, its variant for libraries, while useful and interesting, were not adequate since they are too restrictive. In particular a crucial requirement was that the license should allow commercial companies to use EiffelBase (and other libraries that may use this license in the future) in for-profit developments without any fear (justified or not) that GPL-like requirements could cause proprietary elements of their products to come under the open source umbrella themselves.

The closest model was that of the Perl Artistic License, which significantly influenced the terms of the agreement as shown below. It too, however, was not applicable verbatim. EiffelBase was initially designed as a commercial product and then released as free software, a different situation from that of software that was never commercial.

You will note that there are few restrictions on the use of EiffelBase in the license given below. You can use EiffelBase in your academic work and re-publish the source; you can produce a commercial software product using EiffelBase and not owe a cent to Eiffel Software.


EiffelBase remains an Eiffel Software product and will continue to be distributed as such to Eiffel Software customers. This means in particular that there is no o lessening of our maintenance and support responsibility to our customers under maintenance. In fact, the increased scrutiny and outside contributions will mean an increase of our commitment to develop EiffelBase and of the quality of the product.

The License Text

This is the official license text.


"Eiffel Software" refers to Interactive Software Engineering Inc. "The Library" refers to the collection of software texts in the Eiffel programming language, originally written by Eiffel Software, and constituting the EiffelBase library of fundamental computing science structures, as well as any derivatives of these texts as may be created through textual modification (by people) or through translation to lower-level languages (by programs such as compilers).

"Standard Version" refers to the version of the Library maintained by Eiffel Software and distributed by Eiffel Software to its customers under maintenance.

"You" means any person interested in using, modifying or distributing the Library.

"Source form" means the text of the Library's classes, in the Eiffel programming language.

"Object form" means the translation, as performed by a compiler or other program, of the Library or part of the Library into another, usually lower-level code (such as C, assembly language or machine language) intended for execution by a machine. "Reference implementation" means the latest officially released version of Eiffel Software's implementation of the Eiffel programming language.

Statement of copyright and ownership

1. The Library is the property of Eiffel Software and bears Eiffel Software's copyright. Any use you make of the Library must respect Eiffel Software's proprietary rights.

Right of use

2. Eiffel Software hereby grants you permission to do any of the following without payment to Eiffel Software, under the conditions of sections 3 to 7 of this Agreement:

  • 2.1. Use the Library, in source form or object form, as part of any software you develop and distribute to other parties.
  • 2.2. Distribute the source of the Library to other parties.


3. If you use (2.1) or distribute (2.2) the Library, you are encouraged, but not required,to provide to Eiffel Software and the rest of the Library's user community any bug fixes or other improvements that you make to the existing classes of the Library.

4.If you produce new classes based on the Library or extending the Library, you are encouraged, but not required, to make them available in the same way.

5. If you use the Library (2.1) in source or object form for producing software that you distribute, you are encouraged, but not required, to include the following mention (or its translation into the language of the rest of the distribution, if other than English) in the documentation of your software, including textual documentation as well as online documentation such as "About..." entries:

6. If you distribute the source code of part or all of the Library (2.2) you must:

  • Distribute entire classes, not just extracts.
  • Retain, in the distributed version, the entire copyright notice of these classes.
  • If you need to make any modification to the classes, mark those modifications clearly in the class texts.
  • Ensure that the text remains valid Eiffel. Note that this license does not authorize you to distribute versions of the Library restated in other programming, analysis or design languages, except if mechanically translated from the source form by an Eiffel compiler, in which case they fall under "object form". For any non-mechanical adaptation to other languages you must obtain authorization from Eiffel Software. "Valid Eiffel" includes the language described in the latest edition or printing of the book Eiffel: The Language (Prentice Hall), plus any changes or extensions that have been approved by the Nonprofit International Consortium for Eiffel (NICE) or have been accepted for discussion by the Language Committee of NICE, provided they are accepted by the reference implementation.
  • If Eiffel Software releases a new version of the Library, you must, no later than six months after the release of that version, either: (A) update your distribution to the new version; (B) add the following notice to all files in your distribution:" This is an obsolete version of EiffelBase. The latest version is available from https://eiffel.com"; or (C) cease distributing your version.

You may not charge any fee for the distribution of the Library (source or binary), although you may charge for software that includes the Library in whole or in part as per the other provisions of this Agreement.

7. You may not use the name of Eiffel Software to endorse or promote products derived from the Library without specific prior written permission.



(This list of changes is not part of the license.) General note on changes: as usage of free EiffelBase grows and more people contribute to it, some terms of the license text may occasionally have to be changed in light of this accumulated experience and of comments received from users and contributors. It is our intention to ensure that

  • (1) Any such changes will be minor, affecting the details of the licensing rather than the spirit of IFELL.
  • (2) If they affect the substance of the license in any way, they go in the general direction of extending, not restricting, the rights of users of EiffelBase.

Should a question arise regarding use of EiffelBase, the terms to be applied are those in effect at the time of use, disregarding any later change.

28 June 2000: in response to comments by Joachim Durchholz through Patrick Schoenbach, replacement of most occurrences of the word "EiffelBase" by"the Library" to facilitate application to other libraries.

7 May 1999: in response to comments by David Broadfoot on the Eiffel Software user list, rewording of the explanation of why we are applying more liberal terms than GPL-style licenses. regarding fears of contamination with the Gnu Public License.

6 May 1999: following comments by Ed Avis and Alexander Kjeldaas, we now permit distribution maintainers to continue distributing an old version as long as they mention clearly that it's obsolete .

7 April 1999: following comments by Loryn Jenkins and Ed Avis, removal of the requirement that bug fixes and improvements be provided back to the maintainers of the library. This requirement has been changed to a mere encouragement , facilitating use of the library. Of course it is in everyone's interest to report bugs and improvements.

7 April 1999: following comments by Loryn Jenkins, loosening of the definition of "valid Eiffel" . This change also caused addition of the notion of reference implementation . The purpose is to avoid crippling EiffelBase by preventing it from utilizing innovative language constructs and corrections in the language contributions. Such language extensions are OK as long as they have been accepted for discussion by NICE and are supported by the reference implementation.

1 April 1999: following some comments by Richard Stallman,addition of a qualification (" justified or not") to the notes regarding fears of contamination with the Gnu Public License. Our intention is not to criticize the GPL but simply to note that the GPL does cause some fears, "justified or not", among commercial developers.

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