Con G-keys are programmable only in Windows
In Linux there's absolutely no way to program the G-keys. The only way for that is if the user is in dual boot with operating systems. The software programs the G-keys directly into the keyboard's memory, so those keys work in Linux for as long as Windows is installed.
In case Windows is removed the only keys the keyboard will remember are those using combinations common for both Windows and Linux - such as Ctrl+C, Ctrl+V, Space, Alt+F4 and so on.