Much discussed lately, here are some of his words:

Ed

+++++++++++++++++++++++++++++++++++++++

Indeed, their reports show that there are extensive differences between the two implementations, like Rybka's use of a bitboard. They argue that those changes are mechanical transformations of the Fruit implementation, and therefore not a new implementation of the uncopywriteable algorithms expressed in Fruit but a derivative work in the copyright sense. Lexmark International, Inc. v. Static Control Components, Inc. accepts that conversion of a function to lookup table, or rearranging terms in an expression are not by themselves original acts. However, the transformations in Rybka go well beyond mechanical changes at the call graph level.

They have instead gone up to a higher level of abstraction shown that the code in Fruit, with different input parameters than the Fruit defaults, can generate numbers which after post-processing match numbers used in Rybka. They have stated that the order of certain actions, where the order should be arbitrary, is consistent between the two programs.

While this was enough to convince the judges that Rybka contained unacknowledged algorithmic influence from Fruit in the fashion required by the rules, this argument is not sufficient to show copyright infringement. Here too the comparison method should be validated by applying it to other programs which use the same algorithmic approach as Fruit and which are known to not have a shared copyright history. The Rybka investigators have failed to do this.

Functional similarity by itself does not show copyright infringement. The clean room design model in programming is a well-understood method of using reverse engineering to create a new implementation which does not infringe on copyrights or trade secrets. One group of people reverse engineer the software and develop a design document which is reviewed by a lawyer to make sure that no copyrighted material is included. The document is passed to another group of people to implement, where the people in the second group were selected because they have no knowledge of the original implementation. An real-life example is OpenOffice, which is a clean-room implementation of Microsoft Word and is close enough in functionality that people can switch from one program to the other with little trouble.

Rybka was not developed as a clean-room reimplementation of Fruit, and the author has long acknowledged an intensive review of the Fruit source. The point here is only to show that functional similarity is not a clear indicator of copyright infringement.

Some may believe that reviewing the source code to Fruit means that Rybka is necessarily a derivative work. This is incorrect. A clean-room reimplementation makes it abundantly clear that there is no copyright infringement, but the lack of a clean-room style does not mean there is infringement.

One of the most widely used computer operating systems is Linux, which was greatly influenced by the MINIX operating system. MINIX was available in source form under a proprietary license, and there was a college textbook which described how it worked and included most of the source code. The Linux author studied MINIX and ran MINIX on his computer before developing Linux. The MINIX author stated clearly that Linux is not a derived work in the copyright sense, and no review of the Linux source code has ever shown copyright infringement to any other code, including MINUX.

Therefore, intensive review and study of the Fruit does not mean that Rybka infringes on the Fruit copyright just like an intensive review and study of MINIX does not mean that Linux infringes on the MINIX (or Unix) copyrights.

The Rybka investigators acknowledge that no individual piece of evidence is the proverbial smoking gun. Instead, the pattern of pieces reveals the infringement. The history of evidence synthesis like this is fraught with methodological problems. Quoting from http://en.wikipedia.org/wiki/Meta-analysis#Disadvantages_and_weaknesses:

    The most severe weakness and abuse of meta-analysis often occurs when
    the person or persons doing the meta-analysis have an economic, social,
    or political agenda such as the passage or defeat of legislation. Those
    persons with these types of agenda have a high likelihood to abuse
    meta-analysis due to personal bias. For example, researchers favorable
    to the author's agenda are likely to have their studies "cherry picked"
    while those not favorable will be ignored or labeled as "not credible".
    In addition, the favored authors may themselves be biased or paid to
    produce results that support their overall political, social, or economic
    goals in ways such as selecting small favorable data sets and not
    incorporating larger unfavorable data sets.

There are ways to help offset these problems. For example, all comparison methods should be reported before doing the analysis, along with the definition of what "infringing" means for that case. Methods which fail to report similarity must be recorded. All participants must state possible sources of bias, and the method for selecting the participants must also be published.

This was not done. Of course, if there was strong evidence for copyright infringement then a careful synthesis of the evidence would not be needed, but that was not the case here. Instead, the results seem very much cherry-picked.

It may very well be that Rybka contains copyright infringing code. It's possible, after all, that 27 lines out of 525,000 are enough to make a substantial copyright infringement claim. The problem is that the methodology of the Rybka investigators is not strong enough to be convincing.

They claim to use the abstraction-filtration-comparison test to determine substantial similarity, but without the appropriate filtration. At each of the structural levels they fail to show that the discovery methods are not producing false positives, and they fail to demonstrate that the similarity level is greater than would be expected from a non-infringing chess program implementing the idea at the same structural level.

The similarity between Fruit and Rybka is strongest at the highest level of the analysis, but the abstraction-filtration-comparison test acknowledges that at a high enough level there's no copyright protection. This is due to the merger doctrine.

The document http://www.top-5000.nl/ZW_Rybka_Fruit.pdf is highly misleading. Without a mapping from the C structures based to disassembled code, it's impossible to judge the correctness of what the author writes. With a translation directly into idiomatic Fruit code, the visual similarities are overly distracting from the actual comparison, which is on a level that isn't show.

(You saw in my first email that just because someone reports what the code says, it doesn't mean that that's what the code actually does.)

Copyright law already acknowledges that at higher levels there's no copyright infringement because it's different expressions of a common idea. Hence the statement "high-level functionality is always equivalent in these cases" is meaningless unless it's established that this level is not high enough.