I've been quite sick for more than a week, but finally have a smidge of time to address some issues a bit more.
Your "idea" of a book is not (only) an idea. You can't abstract your expression of this idea without losing the expression "it was the best of times, it was the worst of times".
The context of this has been lost (it came from 6 months ago) I fear, but I think my abstraction was essentially akin to what Schüle was arguing at the time, and Riis mentions (page 18 of his PDF) in his ChessBase series:
But Watkins' evaluation feature is in actuality the formula expressed by an algorithm. This formula is on the conceptual level and therefore, according to accepted practice, everyone is free to use it. Thus his entire analysis lacks traction. I argue that similarly their "formula" is not (only) a formula, but something much more specific than the "conceptual level" they assert.
For instance, I consider something sufficiently broad like "rook on 7th (and 6th/8th)" to be the "concept", and then look at the specific ways that engines express this. As I note in my rebuttal:
But even the example given by Riis fails his purpose: some engines give a rook on 7th bonus all the time; some only do so when the opponent's king is on the 8th or an enemy pawn is on the 7th; some add a bonus for doubled 7th rooks (perhaps depending on whether they mutually guard each other), some for a rook and queen both on the 7th; some have a similar bonus for a rook on the 8th (or even 6th), some don't (see §2.3.5 of EVAL_COMP).
The primary purpose of copyright on software is to protect the source code and object code. Everything going further than that might be "nice to have" for whoever profits from the added protection, but it is not essential for the proper functioning of copyright on software. [...] What is important is that copyright protects the final outcome: the code.
I think we diverge at Point Zero. I start from the fact (good or not) that computer programs are protected as literary works. Thus the "primary purpose" of copyright on computer programs is
exactly the same as for literary works. To barb your phrase the other way: it might be "nice" to not have to worry about such things as nonliteral copying for computer works, but the law states otherwise. You can argue that (for instance), since the primary purpose of copyright is to "promote the Progress of Science and Useful arts", the ensuing public interest generally (greatly) restricts the protection aspects beyond source/object code, but this is still something that needs to be pled specifically in any given case, rather than just assumed.
So as long as Fruit's combination of eval features was created for the purpose of having a good eval and not for expressing Fabien's creative freedom, copying it cannot infringe... (from a copyright point of view).
I think your argument can similarly be applied to the Rorschach inkblots [they were created for a "functional" purpose, and not as an expression of HR's creative freedom]. Am I missing something?
Rule 2 doesn't say that it is copyright that matters, and it is obvious that even if copyright would allow precisely reproducing the functionality of an existing engine, Rule 2 still forbids two engines that make the exact same moves.
Hmm, I think one of the more recent arguments of Riis was (in essence) that Rule 2
should be taken to mean "original" in the copyright sense (at least for
ex post facto application)... About a year ago, Chris Whittington (and maybe Alan Sassler) were arguing similarly regarding the standard in Rule #2. As it was becoming clear that "plagiarism" was going to the the interpretation (rather than copyright), they argued that
surely a commercial programmer like VR should be judged by something closer to a copyright standard than some miasmic ivory-tower invention of the ICGA. A related concern, of how to parse words "original" and "derive/derivative", has also been brought up (by Dalke, and MvK too I think with his code/entry distinction). Dalke went so far as to (in private correspondence) suggest that Levy in his interview deliberately intermixed the casual meaning of derivative with the legal definition (though he also seemed to suggest the latter was poorly-defined, and I must say the USC specification is not too illuminative).