The Eclipse Public License is a weak copyleft licence used by the not-for-profit corporation The Eclipse Foundation on the software projects that it hosts. It is not widely used outside The Eclipse Foundation. However the popularity of the Eclipse Integrated Development Environment (IDE) among both open and closed source developers means that it is a licence that is widely encountered within software development projects. The licence itself can be read at http://www.opensource.org/licenses/eclipse-1.0.txt.
The Eclipse Public License began life in 1999 within the IBM Corporation as the IBM Public License (IPL). IBM were keen to release open source code, but felt that they needed to draft their own new licence to meet their specific needs. Unfortunately the IPL named IBM Corporation as the licensor of code that it covered, meaning that it could not easily be reused by others to cover code their own code. As a result, when IBM came to create a revised version of their licence in 2001 they generalised the terms to remove direct reference to themselves and renamed it the Common Public License (CPL). IBM released their software development platform Eclipse under the CPL in 2001, and at the same time formed a consortium of interested technology companies around the platform including themselves, Borland, SuSE and Red Hat.
By 2003 this consortium had expanded to include over 50 members, and it was decided that the Eclipse platform needed its own legal entity to manage code contributions coming from so many disparate sources. In addition the CPL was revised in two ways to ease the establishment of the Foundation.
Firstly the 'steward' organisation for the licence was changed from being IBM to being the Foundation itself. This helped cohesion of the Foundation's members by ensuring that authority to issue revised versions of the licence in the future - and thus dictate the terms under which the members' code could be used - rested not with a single member but with the Foundation itself.
Secondly it was decided that one term of the so-called 'patent-retaliation' clause within the CPL should be revised. The CPL states that a licensee will lose their licence to use adapt and distribute the code if they start litigation alleging infringement of a patent of theirs by the CPL-covered code. This clause was retained. However the CPL also states that if a licensee starts any software-patent-related litigation against any contributor to the code, then they also lose their licence. This would be true even if the litigation related to some entirely different piece of software. Clearly, with so many large technology players contributing into the Foundation, it seemed overly onerous for them to be restrained from suing each other over any software patent infringements at all, so the clause was deleted.
The CPL has now been retired by IBM, and the Open Source Initiative recommend the use of the EPL in its place.
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