The idea here being that what can be copied in this way is only functionality, and functionality is not copyrightable. So such copying is not "copying" in the sense of copyright law. By chance you could end up with identical source code, but the copyrightable elements in that code have then been independently created.BB+ wrote:In addition, according to the Court, there is no copyright infringement where, as in the present case, the lawful acquirer of the licence did not have access to the source code of the computer program but merely studied, observed and tested that program in order to reproduce its functionality in a second program.
If you did have access to source code, common copyrightable elements in the source code cannot be so easily explained away by the argument of independent creation of the copyrighted elements.
The decision makes clear that everything that is part of the functionality of the program is not copyrightable:For Rybka/Fruit, it seems to me the main contention is what ideas/principles (and "element") means in #30-31
So similarity in expression has to be looked for below the level of the functionality. You have to look for similarity in source code and structure of source code, abstracting away all similarity in functionality.ECJ wrote:40 As the Advocate General states in point 57 of his Opinion, to accept that the functionality of a computer program can be protected by copyright would amount to making it possible to monopolise ideas, to the detriment of technological progress and industrial development.
41 Moreover, point 3.7 of the explanatory memorandum to the Proposal for Directive 91/250 [COM (88) 816] states that the main advantage of protecting computer programs by copyright is that such protection covers only the individual expression of the work and thus leaves other authors the desired latitude to create similar or even identical programs provided that they refrain from copying.
If you look at how Fruit calculates bishop mobility using four loops, the expression can be found in the four loops (of course too trivial to be copyrighted, but that's another point), not in the fact that it counts the number of attacked squares not occupied by friendly pieces. The latter is functionality.