FSF and Eclipse offer guidance on licences
The Free Software Foundation and Eclipse Foundation have released guidance on how each organisations' licenses, the GPL (GNU Public Licence) and EPL (Eclipse Public License), interact with each other. At the core of the debate is the question "Can you GPL an Eclipse plug-in?". The Free Software Foundation Europe were asked in an open letter to clarify wheter it as was possible to create a GPL licensed plugin for the EPL licensed Eclipse platform.
The guidance from both the FSF and Eclipse Foundation is that the licenses are "inherently incompatible", at least in the case of plug-ins. This guidance is based upon the fact that, unlike other GPL software which interacts with Eclipse over pipes or sockets, such as GCC and GDB, plug-ins are effectively "linked" to the Eclipse code.
This linking creates a derivative work in the opinion of the FSF and, as the EPL and GPL are incompatible, the software and its distribution cannot meet the terms of both licenses. The FSF suggest that, where all the copyright holders of GPL covered code in a plug-in agree, that an additional permission be added to the GPL licence to specifically allow linking to Eclipse. This may be quite difficult though, as GPL licensed libraries used would also have to carry the same permission. "Without their permission, incompatibility still exists between their code and the EPL-covered Eclipse libraries" says the FSF's Brett Smith.