Some quick research yields a couple of open source CAS, such as OpenAxiom, which uses the Modified BSD license. Granted that Google has strong "NIH" tendencies,

Some quick research yields a couple of open source CAS, such as OpenAxiom, which uses the Modified BSD license. Granted that Google has strong "NIH" tendencies, but I'm curious why something like this wasn't adapted instead of paying several engineers some undisclosed amount of time to develop a calculation system. The article mentions that a CAS is an order of magnitude (or more!) more complex than the bifurcated rational + RRA approach, as well as slower, but: the complexity would be solved by adapting an open source solution, and the computation speed wouldn't seem to matter on a device like an Android smartphone. My HP Prime in CAS mode runs at 400MHz and solves every problem the Android calculator solves with no perceptible delay. Is it a matter of NIH? A legal issue with the 3-clause BSD license I don't understand? Reducing binary size? The available CAS weren't up to snuff for one reason or another? Some other technical issue? Or, if not that, why not use binary-coded decimal? These are just questions, not criticisms. I have very very little experience in the problem domain and am curious about the answers :)