Boy, am I on some kind of blog binge this week. It’s amazing how a few weeks without travel helps.
Dana Blackenhorn wrote a piece earlier today discussing Matt Asay’s article on why the Apache license is better than the GPL. In his article, he states the following:
If your company wants to release its own code, and control that code, if open source is mainly a marketing concept to you, then a BSD license such as Apache or Eclipse makes perfect sense.
Dana’s statement makes an error that I have seen repeatedly. Namely, that the EPL is a “BSD-style” license and is therefore similar or equivalent to the Apache license. This is just plain wrong. And it worries me that a long-time open source observer such as Dana would make this mistake.
The EPL is what is sometimes referred to as a “weak copyleft” license. It most certainly is a reciprocal license in the same way that the LGPL and the MPL are, for example. (The European Union describes the EPL as a strong copyleft license, in its paper describing license compatibility with the EUPL.)
In our view, the copyleft provisions of the EPL gives our community the best of both worlds. Yes, changes and modifications to EPL-licensed code need to be contributed back. This helps ensure that everyone involved is incented to make their contributions back to the platform, and encourages community building. But at the same time, because the EPL (a) does not define simply linking to it as creating a derivative work and (b) allows re-licensing of binaries under commercial terms, it encourages commercial adoption.
