Via mono. If that's true... that would be an interesting news for the project (not because of the bug itself of course...).
But the team in Microsoft Research are (a) keen to promote their language (people like Don and Brian often help early adopters personally) and (b) supportive of Mono (they've always released a .zip file for Mono at the same time as their Windows installers).
http://www.computerworlduk.com/news/open-source/3260727/lond...
I suspect that if there is any F# code, it's in a 3rd party system that talks to the stock exchange. There are lots of those due to the nature of an exchange, though they should all talk over the standard FIX protocol.
Why not? What makes you think this is a lie?
On the other hand, it has to integrate with lots of enternal trading systems, one of which could easily be written in F#.