Yes.
But I guess, Russian distributor also contributes for good of all users. There is Russian hyphenation in Coolreader.
Even I or other participants of this forum have helped all Onyx users (even Arta Tech) ones. We completely, or partially translated user interface to our languages.
Booxstor promised me a small discount in his shop as thanks for my work. I did not get any thanks from Arta Tech for my work, not speaking about some financial benefit. And guy from Arta Tech reads/used to read this Onyx forum...
I do not know if Icarus is the top model from M92 line. If yes, there should be no problem to install Booxstor firmware. I know there used to be problem to install it on lower models of M92 (without audio output, without touch screen capability). The problem was that instalation procedure checked if there is hardware expected and there was not - things were missing. So, instalation procedure was interupted. If you are interested in details, ask in Russian thread in this Onyx forum.
I would not say the Boxstor firmware is official Onyx firmware. It is rebranded official Onyx firmware. I do not know what exactly is Booxstor's position in firmware development. But I know for sure that he can manage that things are fixed and/or changed. I experienced it many times. So, he must have quite a influence on SW development.
But it is not important.
I see you acknowledge importance of firmware development, so you may support it by buying M92 in Booxstor's. It is just 10-20 EUR more. Few beers.