I wonder what are the societal attitude of these countries towards these traders. Some people look down on traders because they feel they are not socially useful.
If you believe in free markets and the efficacy of such to best determine the value of a thing, then traders (speculators) make markets and provide liquidity and reduce risk of lesser risk takers such as investors and hedgers. If you believe in a command economy and that prices should be set through a bureaucratic process then you would likely be opposed to speculation.
Most professional traders use servers that are running some Linux-type OS. These are the servers that actually route orders to the exchange. For desktops to input orders/view GUIs, it varies. Id imagine the most retail traders are using Windows. Note that most retail brokerages don't offer Linux based platforms, which is likely a matter of demand.
There are 1,267,398,634 active traders in the world as of 31st Dec 2016. These numbers are from the United Nations study of traders.