He paid for membership, not for the board seat.
You'd think the other board members could have silently replaced the seat with an electric chair by now.
They're quite a bunch anyway. I speculate that Karpeles still holds the seat only because he knows uncomfortable secrets about each one of them but Jon Matonis and Gavin.
This is becoming too much of a conspiracy theory

.
He's holding that seat because nobody till know had a real reason to throw him out , nor a replacement.