"market share", yea
... and here we have a fail, right there.
"Market" is defined as units sold. How do you measure market for a software which is not sold?
Or is that number meaningful at all when every hardware piece force sells one unit regardless of actual use?
Basically every Linux machine in work has Windows licence sticker on it even it's not used at all because you can't buy PC:s without Microsoft tax.
So no, "market share" is basically irrelevant number.