Chapter 3. eCos Licence Overview

As of May 2002, eCos is released under a modified version of the well known GNU General Public License (GPL), now making it an official GPL-compatible Free Software License. An exception clause has been added to the eCos license which limits the circumstances in which the license applies to other code when used in conjunction with eCos. The exception clause is as follows:

 As a special exception, if other files instantiate templates or use macros
 or inline functions from this file, or you compile this file and link it
 with other works to produce a work based on this file, this file does not
 by itself cause the resulting work to be covered by the GNU General Public
 License. However the source code for this file must still be made
 available in accordance with section (3) of the GNU General Public
 License.

 This exception does not invalidate any other reasons why a work based on
 this file might be covered by the GNU General Public License.

The goal of the license is to serve the eCos user community as a whole. It allows all eCos users to develop products without paying anybody anything, no matter how many developers are working on the product or how many units will be shipped. The license also guarantees that the eCos source code will always be freely available. This applies not only to the core eCos code itself but also to any changes that anybody makes to the core. In particular, it should prevent any company or individual contributing code to the system and then later claiming that all eCos users are now guilty of copyright or patent infringements and have to pay royalties. It should also prevent any company from making some small improvements, calling the result a completely new system, and releasing this under a new and less generous license.

The license does not require users to release the source code of any applications that are developed with eCos. However, if anybody makes any changes to code covered by the eCos license, or writes new files derived in any way from eCos code, then we believe that the entire user community should have the opportunity to benefit from this. The license stipulates that these changes must be made available in source code form to all recipients of binaries based on the modified code, either by including the sources along with the binaries you deliver (or with any device containing such binaries) or with a written offer to supply the source code to the general public for three years. It is perhaps most practical for eCos developers to make the source code available online and inform those who are receiving binaries containing eCos code, and probably also the eCos maintainers, about the location of the code. See the full text of the GPL for the most authoritative definition of the obligations.

Although it is not strictly necessary to contribute the modified code back to the eCos open source project, we are always pleased to receive code contributions and hope that developers will also be keen to give back in return for what they received from the eCos project completely free of charge. The eCos maintainers are responsible for deciding whether such contributions should be applied to the public repository. In addition, a copyright assignment is required for any significant changes to the core eCos packages.

The result is a royalty-free system with minimal obligations on the part of application developers. This has resulted in the rapid uptake of eCos. At the same time, eCos is fully open source with all the benefits that implies in terms of quality and innovation. We believe that this is a winning combination.