Yeah right now the issue, while the package is a great start (thanks SimonLothar), is that people are forced to register an account on Casio website to download Casio FX-9860G SDK, which the PRIZM mini-SDK is dependent on. Casio site is slow from North America and on top of that, you need to enter your 9860G serial number. If you don't have a FX-9860G, you must find a serial illegally. What we need eventually is a C SDK that has no dependencies on anything: Just click a setup.exe and it's done installing or something close.
Later, I guess a 3rd-party language like Axe might be welcome. Let's not forget SH3 ASM of course, for those who prefer lower level stuff, but C is definitively gonna be a must for developers because if you check 68K and ARM9 calcs, most people code in C.