Hello from the Clojure community! We use EPL pretty widely and Mike was nice enough to drop us a line on the mailing list about the proposed changes. I talked to Rich Hickey about it briefly and wanted to pass on some feedback. I'll preface it by saying that we're happy with EPL 1.0 as is.
Re "Definition of Derivative Works", there is no clear statement about what problem needs to be addressed. The previous thread said that "Relying on the term "derivative works" as defined in US law has been an issue in a number of scenarios, particularly in Europe." That hints at the problems but does not state what they actually were.
A potential solution is "Changing this to a defined term would help be explicit about what we mean. We would recommend using the definition from the ALv2 license, perhaps with an explicit inclusion of sub-classing." but no other potential solution was offered for consideration.
Currently, EPL derives its power from copyright. Without a definition of derived work, the definition of US copyright is presumed, which includes all legal precedents associated with it. With a definition, the EPL becomes more like a contract and legal challenges would fight about what it contains, with no precedents. Perhaps the use of US copyright law is related to the problems in Europe?
ALv2 is perhaps not the best place to look for precedent in this because it is not a reciprocal license and thus cares about derivative works primarily for notice conveyance, which is a different problem with different concerns. ALv2 just defines derives works as "based on (or derived from)" which doesn't really clarify anything. The exclusion in the ALv2 license might be useful though: "For the purposes of this License, Derivative Works shall not include works that remain separable from, or merely link (or bind by name) to the interfaces of, the Work and Derivative Works thereof."