When the on-screen Redux keyboard keys are clicked, they show as such by becoming grey and a sound is made. When the computer keyboard is used, the corresponding on-screen key becomes grey, but no sound is heard. Seems (sounds) like a bug. Redux demo version, Linux Mint 17, Redux used as a plugin for Ardour. External MIDI keyboard works fine.
Edit: As I follow along the Quick Start, the Esc and TAB keys do not work, to edit and move along columns, as they do in Renoise. I think it would be safe to say that the computer keyboard does not work at all, even though, when trying to play a sample, the corresponding key is greyed out (eg. pressing ‘z’ will make the hexagonal on-screen ‘z’ become grey). This means that Redux recognizes the computer keyboard, and that there’s a problem further down in processing. As such, it is not possible to buy Redux with this problem.
I do have Renoise 3 on the same machine and everything works just fine.