What exactly gives Davis a better claim to the copyright than the inventors of the algorithm? Yes, I know software is copyrightable while algorithms are not, but it is not at all clear to my why that should be the case. The effort of translating an algorithm into code is trivial compared to designing the algorithm in the first place, no?
Copyright is formed when a human makes a choice about equivalent ways of implementing an algorithm.
For example, it would interfere with e.g. copyright of scientific/mathematical papers if algorithms were copyrightable, as mathematicians would not be able to extend another mathematician’s ideas without first gaining permission.