Actions like these will kill the whole arduino brand. It's akin to parents that divorce claiming a physical half of their kids each, it simply will not work.

The rest of the world needs to see a unified front and to air your dirty laundry like this in an attempt to pre-empt the lawsuit is only going to turn off the recipients of this letter from the arduino brand and will cause them to look for alternatives elsewhere (of which there are quite a few by now).

What a pity, the arduino brand had a ton of goodwill attached.