[mistakes]

You say he contributed nothing to your current product

Actually, I said

A's contribution to our current efforts is zero

It's an important difference and I chose the word carefully. Our early efforts with him did not succeed, but based on my experience it is almost impossible to succeed without making mistakes first and learning from them. We value his contribution, which is why I am trying to determine a fair way to compensate him for this efforts.

Edit: Let me expand on what I said. It is hard to talk about separation while sounding entirely positive, because separation is not a positive event. I wouldn't even have met my other cofounder if it were not for A. So, rest assured, however this separation is structured, in my mind he will have earned his keep.